Explanation: We can figure out this answer by using simple process of elimination. The first answer is clearly incorrect because it is not a deciding factor of survival. The pitch of it's croak will not change anything. So there is no reason they will be eliminated. The third answer is also incorrect because since the higher pitch does not help the frog's survival, there will be no need for adaptation towards higher pitch. This is the same for the fourth answer. So the answer must be B.
