Answer:
Option B, extinction can be related to a failure to adapt to changes in the environment.
Explanation:
Here,
The toads species became extinct as the pools used by them for breeding dried up. If these toad would have adapted themselves to mate even in dry condition or without water they would have survived.
Drying up of pool is a natural event resulting into change in native environment.
Option A is not correct as in this scenario as there were no native species other than the toads which were consuming the resource
Also option C, is not correct as in this scenario the extinction was not related to infection caused by any microorganism like bacteria etc.
Option D is also incorrect as there was no involvement of humans, which had led to the drying up of pool.
Thus, only option B is a possible answer to this question