Answer:
C). But they can control these pests.
Explanation:
As per the question, the most appropriate revision of the underlined phrase would be 'but they can control these pests' as it involves the pronoun 'they' forthrightly refers to 'farmers' and thus, it does not contain any ambiguity and convey a clear and coherent meaning. The other options either employ an incorrect pronoun referent(in options A and B) or either offers an inappropriate meaning(option D) or completely transforms the structure and meaning unnecessarily(option E due to use of 'except'). Thus, <u>option C</u> is the correct answer.
Most of the competition that occurs in our ecosystem is basically just for survival. Breaking down into food supply, shelter, mate, etc. For frogs and birds, the thing that they are competing is the food supply. Given that they could live very near to each other, they will be competing for insects or other smaller animals.