Farmers greatly increase the number of pests by providing them with a uniform food source in the form of large areas of single-crop vegetation, but these pests can be controlled when they use synthetic, or better yet, biological pest controls. A) but these pests can be controlled
B) but these pests are controllable
C) but they can control these pests
D) which can be controlled
E) except that can be controlled

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, option C is the correct answer.

i   believe   the   answer   is   d

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