Read the sentence below to find out whether there is any grammatical error in it. The error, if any, will be in one part of the sentence. Choose the option with that part as your answer. If there is no error, choose 'D' as your answer. (Ignore the errors of punctuation, if any).

Happily, zoos were unwilling to cooperate in a scheme that was potentially harmful to animal welfare

A.

Happily, zoos were

B.

unwilling to cooperate

C.

in a scheme that was potentially harmful to animal welfare

D.

No error.

Correct answer is C

on a scheme that was potentially harmful to animal welfare