Paleontologist: About 2.8 million years ago, many species that lived

This is quite a challenging BF question and the variety of responses here support my belief.

Understanding the Passage

Let's start with something we should do first i.e. understanding the passage. Let's go through the passage line by line:

1. About 2.8 million years ago, many species that lived near the ocean floor suffered substantial population declines. - It's a factual statement that tells us something that happened a long time ago.

2. These declines coincided with the onset of an ice age. - This is also factual. However, this fact happened at the same time as the one in first statement.

3. The notion that cold killed those bottom-dwelling creatures outright is misguided, however; - Now, this is Paleo's opinion. Saying that someting is misguided is not a fact, it's an opinion that tells us that Paleo doesn't agree that cold killed those bottom dwelling creatures.

4. temperatures near the ocean floor would have changed very little. - This is a reason to back up the opinion of Paleo. Since the temperatures changed very little, this temperature change should not have led to the death of bottom dwelling creatures.

5. Nevertheless, the cold probably did cause the population declines, though indirectly. - This is our first Bold Face statement or BF1. This is a causative statement where the Paleo links cold to population decline, with a keyword "indirectly". So, in previous statement, the Paleo opined that cold did not lead to death of bottom dwelling creatures and provided a reason for the same. In this statement, Paleo introduces his own theory of how cold might have effected bottom dwelling creatures. So, this statement could be called an opinion or conclusion or judgement or hypothesis of the Paleo.

6. Many bottom-dwellers depended for food on plankton, small organisms that lived close to the surface and sank to the bottom when they died. - This is most probably a fact because what bottom creatures eat is not a matter of opinion, they eat what they eat. However. the presence of "many" could make it an opinion since different people would define "many" differently. This statement, along with the next statement (BF2) provides support to the opinion of the Paleo (BF1). This statement says that bottom dwelling creatures depended on Plankton for food.

7. Most probably, the plankton suffered a severe population decline as a result of sharply lower temperatures at the surface, depriving many bottom-dwellers of food. - This is BF2. This says that Plankton suffered a sever population decline. Read this statement with the preceding statement, which said Plankton was food for bottom dwelling creatures. So, combining these statements, we find that the food of bottom dwelling creatures declined severely. This could now explain BF1 (indirect cause of decline).

Now, let's look at the options:

Option Analysis

A. The first introduces the hypothesis proposed by the paleontologist; the second is a judgment offered in spelling out that hypothesis. - As we understand, BF1 can be termed as hypothesis of Paleontologist. We know BF2 supports BF1. So, the roles of both BF1 and BF2 roughly match with our understanding. Let's keep this option in the fray.

B. The first introduces the hypothesis proposed by the paleontologist; the second is a position that the paleontologist opposes. - Here, the explantion of BF2 is easily wrong. Paleo doesn't oppose BF2 in any way. Thus, this is incorrect.

C. The first is an explanation challenged by the paleontologist; the second is an explanation proposed by the paleontologist. - Here, BF1 is not challenged by the Paleo; instead, BF1 is proposed by Paleo. So, Incorrect.

D. The first is a judgment advanced in support of a conclusion reached by the paleontologist; the second is that conclusion. - In our anlaysis we found that BF2 supports BF1 and this option says just the opposite. However, I would advise you to eliminate this option only after reading BF1 and BF2 again. But do eliminate this because BF1 is no way explain BF2. So, this is also incorrect.

E. The first is a generalization put forward by the paleontologist; the second presents certain exceptional cases in which that generalization does not hold. - BF2 doesn't present any exceptional circumstances. Therefore, this is also incorrect.

So, after going through the options, we find that option A is the correct choice.

Hope this helps

Let me know in case of further queries.

Thanks,
Chiranjeev