The passage does not refer to biologists, much less citing the views of other biologists - the author refers to ecologists. I kept reminding myself that I can’t violate word of zeus. Doesn’t the passage require us to use outside knowledge in this question? Correct answer is D. Why are A and C wrong in this question?
Yes, I believe outside knowledge can help with solving this problem, but it’s not the only way.
Outside Knowledge
The first line in the passage refers to the views of Gilbert White and (Charles) Darwin. Darwin is the more recognizable name here, and if one knows what Darwin is famous for, one would also know that Darwin was a biologist.
Additionally, ecology is a branch of biology, so any reference to ecologists should count as a reference to biologists.
Word of Zeus
The second sentence states:
“The task for ecologists is to untangle the environmental and biological factors that hold this intrinsic capacity for population growth in check over the long run.”
While working with “biological factors” does not necessarily make someone a biologist, both answer choices A and C make reference to biologists. At lease one of these choices must be correct, which means at least some of the people mentioned must be biologists.
Using the quoted sentence, one can then infer that, at a minimum, ecologists are a type of biologist, and further, that White and Darwin are biologists as well, since their observations on species population growth underpin a major facet of ecology.