We know many scientists believe that air pollution enhanced the strength of El Nino. But the stimulus never confirms this belief is true.

We know that fires were unusually large and intense due to the unusually strong El Nino. This doesn’t imply that if the El Nino weren’t as strong, there would only be “few” large/intense forest fires. Perhaps there would not be as many, or the fires would be less large/intense; this doesn’t imply there would only be “few,” however.

We have information about one year: 1997. That year had an unusually strong El Nino, and the fires were unusually large and intense. But a single data point doesn't support a claim about what is "generally" the case during strong El Ninos.

The stimulus tells us what scientists believe about the El Nino's strength: that air pollution enhanced it through global warming. But the stimulus says nothing about what scientists believe about the fires. Although we know from the stimulus that the unusually strong El Nino contributed to the unusually large and intense fires, we don't know whether scientists are aware of that fact.

We know that the strong El Nino caused the drought. So if air pollution strengthened the El Nino, then air pollution also played a causal role in producing the drought.

Notice that (E) doesn't assert that air pollution did strengthen El Nino. It only says what would follow if air pollution strengthened El Nino. That's an important distinction, because it means (E) doesn't require us to treat the scientists' belief as fact.

To hammer this point home, imagine that (E) doesn't start with "if." Instead, it states, "Air pollution contributed to the widespread drought in 1997." In that case, (E) would be wrong for the same reason that (A) is wrong. It would be treating the scientists' belief as fact.

Now imagine that (E) states "Scientists believe that air pollution contributed to the widespread drought in 1997." In that case (E) would be wrong for the same reason that (D) is wrong. It would be assuming that the scientists are aware of the fact that the El Nino contributed to the unusually large and intense forest fires.