If the answer choices make no sense to you, you didn’t read the passage carefully.

Core concept:
Biologist Ari Martinez and colleagues, who studied the ecological community the species share, hypothesized that there is an inverse relationship between birds' field of vision while foraging and their sensitivity to alarm calls from neighboring species.

An inverse relationship is when one variable increases (UP) while the other decreases (DOWN).
Thus, it can be concluded that the wider the field of vision, the lower the sensitivity to sound.

The text says that M. Barbatus forages in relatively dense vegetation, which means it has narrower field of vision (plants limit visibility because they block the line of sight).

In contrast, P. Saturatus forages in open areas or low-density vegetation (it is logical that you can see more and farther in open areas).

A) contradicts the hypothesis. If neither reacts, there is no inverse relationship at all.
B) shifts focus to other species, not the comparison between M. barbatus and P. saturatus. The text gives NOT the slightest hint of any other birds, so you can cross that option out right away
C) Firstly, the text generalizes M. barbatus and P. saturatus, so we cannot refer to ‘some individuals’. It is either all or none. Secondly, P. Saturatus should not react to the sound because it has low sensitivity.
D) directly matches the hypothesis species by species; compares birds with different fields of vision reacting differently to the same alarm call; tests the predicted mechanism.