The southern half of a certain region of the earth was covered entirel

Question

The southern half of a certain region of the earth was covered entirely by water during the Cretaceous period, the last 75 million years of the Mesozoic era, the era when dinosaurs roamed the earth. Dinosaurs lived only on land. Thus, Plesiosaurs—swimming reptile that lived during the Cretaceous period exclusively—were not dinosaurs. No single species of dinosaur lived throughout the entire Mesozoic era.

If the statements in the passage are true, each of the following could be true EXCEPT:

(A) Dinosaurs inhabited the northern half of the region throughout the entire Mesozoic era.

(B) Plesiosaurs did not inhabit the southern half of the region during the Cretaceous periods.

(C) Plesiosaurs did not inhabit the southern half of the region before the Cretaceous period.

(D) Dinosaurs did not inhabit the northern half of the region during the Cretaceous period.

(E) Dinosaurs inhabited the southern half of the region throughout the entire Mesozoic era.

GDT · Accepted Answer

(A) Dinosaurs inhabited the northern half of the region throughout the entire Mesozoic era.  Incorrect. It can be true. It is important to note that we are given in text that no single species of dino lived throughout but here we are given Dinos as a whole So, it is possible

(B) Plesiosaurs did not inhabit the southern half of the region during the Cretaceous periods.  Incorrect. it can be true. We are given that they were swimming reptiles So, they must have lived in water. But we are not given if the southern half of that region was the only place where water was present

(C) Plesiosaurs did not inhabit the southern half of the region before the Cretaceous period.  Incorrect. It can be true. We are given that they lived during Cretaceous period so, it is possible that they were not present before this period

(D) Dinosaurs did not inhabit the northern half of the region during the Cretaceous period.  Incorrect. It can be true if no species lived at that time because we already know that during this time Southern half was filled with water

(E) Dinosaurs inhabited the southern half of the region throughout the entire Mesozoic era.   Correct. It can't be true because we know that during Cretaceous period, southern half was entirely covered by water. So, during this time dinos couldn't have lived in Southern half

HarshaGM · Answer

The correct answer is option (E).

Gist of the passage: 
1. Mesozoic era: Period of time when dinosaurs roamed the earth
2. Cretaceous period: The last 75 million years of the Mesozoic era
 a) In this period, the southern half of a certain region of the earth was covered entirely by water (i.e. no land)
 b) Plesiosaurs, a swimming reptile lived during this period exclusively
3. Dinosaurs lived only on land
4. No species of dinosaur lived throughout the entire Mesozoic era i.e. some species perished in this time period (entire Mesozoic era)
5. Conclusion: Plesiosaurs were not dinosaurs.

Question:  Find the one statement that cannot be true (the other statements may be true -> not must be true)

(A) Dinosaurs inhabited the northern half of the region throughout the entire Mesozoic era. 
This may be true. Even in the last 75 million years, the northern half of the region was still land. Which means it is possible that dinosaurs inhabited this area. So, it is possible that throughout the entire Mesozoic era, dinosaurs in general inhabited the northern half. 
Note that no dinosaur species survived the whole Mesozoic era, but the option talks about dinosaurs in general, not a species of dinosaur. Hence, this statement can be true i.e. not necessarily false.

(B) Plesiosaurs did not inhabit the southern half of the region during the Cretaceous periods. 
During the cretaceous period, the southern half of the region was water. Plesiosaurs could survive in water => it was possible for them to inhabit this region. 
But it is also possible that they inhabited other watery regions on planet earth, and not this region. We only know that Plesiosaurs lived during this time period, we do not know whether they lived in this region. It may be possible that no plesiosaur lived in this entire region. Hence, this statement is not necessarily false.

(C) Plesiosaurs did not inhabit the southern half of the region before the Cretaceous period. 
Plesiosaurs lived during the Cretaceous period exclusively. i.e. they were not around before the Cretaceous period. Hence, this statement is definitely true. Hence, not a false statement

(D) Dinosaurs did not inhabit the northern half of the region during the Cretaceous period. 
This could be true. We know that dinosaurs could not have inhabited the southern half of the region. They could have inhabited the northern region. However, it is also possible that the dinosaurs did not inhabit the northern half also and inhabited other regions of the earth. That may also be true. Hence, this statement is not necessarily false.

(E) Dinosaurs inhabited the southern half of the region throughout the entire Mesozoic era. 
Bingo! This is impossible given the facts of the passage.

We know for sure that dinosaurs could not have inhabited the southern region during the last 75 million years (Cretaceous period). Hence, this statement is definitely false.

Cheers!

ramalcha · Answer

This is an interesting question that presents a set of facts that we can break down to eliminate each answer choice:

1. Mesozoic era - the  whole era  in which dinosaurs lives
2. Cretacious period -  the last  75 million years of the Mesozoic era (a subset of the whole era)
3. Southern half of the region was covered  entirely by water  during  Cretacious period 
4. Dinosaurs  only  lived on land
5. Plesiosaurs - swimming reptile therefore not a dinosaur - lived in the cretacious period  exclusively 
6. No  single  species of dinosaur lived throughout the whole Mesozoic era

(A) Dinosaurs inhabited the northern half of the region throughout the entire Mesozoic era.
 Given in facts 3 and 4 - Eliminate

(B) Plesiosaurs did not inhabit the southern half of the region during the Cretaceous periods.
 Tricky one but there was no fact that stated that there were was no water in the northern region, so Plesiosaurs could have inhabited in the northern half of the region - Elminate
 
(C) Plesiosaurs did not inhabit the southern half of the region before the Cretaceous period.
 Clearly stated in Fact 5 - Eliminate
 
(D) Dinosaurs did not inhabit the northern half of the region during the Cretaceous period.
 Given in Facts 2, 3 and 4 - Eliminate

(E) Dinosaurs inhabited the southern half of the region throughout the entire Mesozoic era.
 This statement presents a contradiction between Facts 3 and 4. Since Dinosaurs  only  lived on land, and since in the Cretacious period (a period within the Mesozoic era) the southern half of the region was covered  entirely by water , it is impossible to conclude that dinosaurs inhabited the southern half of the region throughout the  entire  Mesozoic era - Correct answer

GmatKnightTutor · Answer

If we distill this passage down we get a few statements: Southern half of some region was covered by water during a period when dinosaurs lived. Dinosaurs only lived on land. Thus some swimming reptile was not a dinosaur. No single dinosaurs species lived throughout this period.

The southern half of a certain region of the earth was covered entirely by water during the Cretaceous period, the last 75 million years of the Mesozoic era, the era when dinosaurs roamed the earth. Dinosaurs lived only on land. Thus, Plesiosaurs—swimming reptile that lived during the Cretaceous period exclusively—were not dinosaurs. No single species of dinosaur lived throughout the entire Mesozoic era.

If the statements in the passage are true, each of the following could be true EXCEPT:

(A) Dinosaurs inhabited the northern half of the region throughout the entire Mesozoic era.
Dinosaurs live on land. The northern half of the region may have been water free during the entire M era. This leaves open the possibility for dinosaurs to live there throughout.

(B) Plesiosaurs did not inhabit the southern half of the region during the Cretaceous periods.
P are not dinosaurs; they are swimming reptiles that lived during the C period. It is entirely possible that they swam/inhabited in the southern region covered by water therefore.

(C) Plesiosaurs did not inhabit the southern half of the region before the Cretaceous period.
This COULD be possible, since the argument is effectively only confirming that the region was covered in water during the Cretaceous period only. We don't know for sure what the water situation was before or after that period.

(D) Dinosaurs did not inhabit the northern half of the region during the Cretaceous period.
The question is asking what COULD be true. And we know nothing about the northern part of the region. The passage, I daresay, heavily implies that only the southern part was covered in water, so it's possible dinosaurs lived in the north.

(E) Dinosaurs inhabited the southern half of the region throughout the entire Mesozoic era.
Well, the argument is saying the southern half was covered by water and dinosaurs lived only on land. So... yeah... this one can't be true.

Some Kudos would be nice

Azakura16 · Answer

Background: The southern half of a certain region was entirely underwater during the Cretaceous period.
Background: The Cretaceous period was the last 75 million years of the Mesozoic era, which was the era when dinosaurs roamed the earth.
Background: Plesiosaurs were swimming reptiles that lived exclusively during the Cretaceous period.
Premise: No single species of dinosaur lived throughout the entire Mesozoic era.
Premise: Dinosaurs lived only on land.
Conclusion: Plesiosaurs weren’t dinosaurs.

A. Could be true, as the northern half wasn’t necessarily underwater.
B. Could be true. Just because they live in the water and the southern half of the region was underwater doesn’t mean that they were automatically inhabiting the area. 
C. This is true, because Plesiosaurs didn’t exist before the Cretaceous period.
D. Could be true. Again, just because dinosaurs could live somewhere doesn’t mean they did.
E. This couldn’t be true, because the southern half of the region was underwater during the Cretaceous period, which was part of the Mesozoic era, and dinosaurs live only on land.

Sandeepgurwa · Answer

Option A and E are the only option which contradict each other. Therefore, one of then is the answer to this question. And in the first line of the passage it is clearly stated that Southern half of the certain region was entirely covered with Water and Dinosaur live on land. Therefore, E is the correct answer choice to this question.

The southern half of a certain region of the earth was covered entirel

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The southern half of a certain region of the earth was covered entirel

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