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Answer: (C)

(A): Wrong verb tense. Since the first part is written in the present tense ("is"), it doesn't make sense to suddenly change to a past tense voice.
(B): Wrong tense, and wrong adverb ("increasing").
(C): Correct. No grammatical errors.
(D): Wrong verb tense. Usage of past perfect here is not appropriate.
(E): Verb tense selection is okay, but same issue with adverb as seen in (B).
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E
Since... use "have been observed..."
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Answer: C

Split: increasing vs increased
since it relates to only once type of carbs its increased mortality rates. its not a varying rates, its a rate overall. hence B and E eliminated.
have been correct tense.
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Bitter crab disease is a parasitic infection that poses a significant danger to crustacean fisheries, since infected crabs were observed to have increased mortality rates as high as 86 percent.

(A) were observed to have increased mortality rates
Use of were is wrong since this talking about present

(B) were observed to have increasing mortality rates
Use of were is wrong since this talking about present

(C) have been observed to have increased mortality rates
Correct use of tense and modifier increased

(D) had been observed to have increased mortality rates
There is no past event to be preceded

(E) have been observed to have increasing mortality rates
Use of increasing is wrong as it sows continuity

Ans C
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'Since' means we need present perfect tense

(A) were observed to have increased mortality rates
Out because we need present perfect tense

(B) were observed to have increasing mortality rates
Out because we need present perfect tense

(C) have been observed to have increased mortality rates
Looks ok, no error

(D) had been observed to have increased mortality rates
Out because we need present perfect tense

(E) have been observed to have increasing mortality rates
Have increasing is wrong, it should ' have been increasing'. Out

So c is our answer
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Bitter crab disease is a parasitic infection that poses a significant danger to crustacean fisheries, since infected crabs were observed to have increased mortality rates as high as 86 percent.

(A) were observed to have increased mortality rates ~ Main clause is present tense, so subordinate clause also should follow present tense. Use of were observed is incorrect.

(B) were observed to have increasing mortality rates ~ Main clause is present tense, so subordinate clause also should follow present tense. Use of were observed is incorrect.

(C) have been observed to have increased mortality rates ~ Correct usage of present tense and have increased

(D) had been observed to have increased mortality rates ~ Main clause is present tense, so subordinate clause also should follow present tense. Use of had been observed is incorrect.

(E) have been observed to have increasing mortality rates ~ Increasing mortality rate means that the mortality is still increasing which is not correct.


IMO C.
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Bitter crab disease is a parasitic infection that poses a significant danger to crustacean fisheries, since infected crabs were observed to have increased mortality rates as high as 86 percent.
The main clause of the sentence is in the present tense, so the subordinate clause should also follow present tense format.
Option A, B and D are out.
increasing mortality rates implies the enhancement in rates are still on-going. Option E is out.
Option C is the most appropriate choice.
Answer C
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12 Days of Christmas 🎅 GMAT Competition with Lots of Questions & Fun

Bitter crab disease is a parasitic infection that poses a significant danger to crustacean fisheries, since infected crabs were observed to have increased mortality rates as high as 86 percent.

(A) were observed to have increased mortality rates
(B) were observed to have increasing mortality rates
(C) have been observed to have increased mortality rates
(D) had been observed to have increased mortality rates
(E) have been observed to have increasing mortality rates


 


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Bitter crab disease is a parasitic infection that poses a significant danger to crustacean fisheries, since infected crabs were observed to have increased mortality rates as high as 86 percent.

(A) were observed to have increased mortality rates
(B) were observed to have increasing mortality rates
(C) have been observed to have increased mortality rates
(D) had been observed to have increased mortality rates
(E) have been observed to have increasing mortality rates

Increasing vs Increased

(A) were observed to have increased mortality rates
-- 'were observed' refers to an action in the past. Incorrect usage here

(B) were observed to have increasing mortality rates
-- incorrect use of 'increasing'

(C) have been observed to have increased mortality rates
-- correct usage

(D) had been observed to have increased mortality rates
-- 'had been' is incorrect tense usage here

(E) have been observed to have increasing mortality rates
-- incorrect use of 'increasing'

Option C
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Answer:A

(A) were observed to have increased mortality rates
(B) were observed to have increasing mortality rates
(C) have been observed to have increased mortality rates
(D) had been observed to have increased mortality rates
(E) have been observed to have increasing mortality rates
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(A) were observed to have increased mortality rates present tense required
(B) were observed to have increasing mortality rates present tense required
(C) have been observed to have increased mortality rates Correct
(D) had been observed to have increased mortality rates present tense required
(E) have been observed to have increasing mortality rates increasing rate at 86% seems wrong


IMO C
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Bitter crab disease is a parasitic infection that poses a significant danger to crustacean fisheries, since infected crabs were observed to have increased mortality rates as high as 86 percent.

(A) were observed to have increased mortality rates
(B) were observed to have increasing mortality rates
(C) have been observed to have increased mortality rates
(D) had been observed to have increased mortality rates
(E) have been observed to have increasing mortality rates

Solution: The original underlined phrase uses wrong tense i.e. Past tense. Since is used here and hence it should have a present perfect tense following it. Also 'Increased' mortality rates is wrong as it doesn't mention anything about previous mortality rates. It should be increasing.

(A) were observed to have increased mortality rates
Explanation: As discussed above, it is wrong. INCORRECT

(B) were observed to have increasing mortality rates
Explanation: Similar error as in option A regarding the use of tense. INCORRECT

(C) have been observed to have increased mortality rates
Explanation: Here present perfect tense is used which is right. The observation happened in the past and is continuing in the present. But 'increased' is the wrong form of verb used here. INCORRECT

(D) had been observed to have increased mortality rates
Explanation: Here past perfect tense is used which is not right. The observation happened in the past and past perfect cannot be used to express a single past event. INCORRECT

(E) have been observed to have increasing mortality rates
Explanation: Here present perfect tense is used which is right and 'increasing' is used which is also right. CORRECT

Hence, Option E is the right choice.
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C.

'have been observed' rather than 'were/had been' is correct as the phenomenon is occurring still in the present, not just in past
'increased mortality' is correct, not 'increasing'-meaning changed
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Bitter crab disease is a parasitic infection that poses a significant danger to crustacean fisheries, since infected crabs were observed to have increased mortality rates as high as 86 percent.

(A) were observed to have increased mortality rates => "were observed" wrong tense usage here
(B) were observed to have increasing mortality rates => "were observed" wrong tense usage here
(C) have been observed to have increased mortality rates => OK. Present perfect is okay. The beginning of the sentence is in present tense
(D) had been observed to have increased mortality rates => no need to have past perfect here. The beginning of the sentence is in the present and past perfect + present perfect after makes no sense.
(E) have been observed to have increasing mortality rates => "have increasing" makes no sense.

so answer C
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