The correct option is A c
The option that has an error, is the correct option.
Option C: The
error lies in part (c): 'or capable'. 'Or' is the error here.
The conjunction 'neither' will always be paired with 'nor', as it refers to two alternatives in the negative.
Also, 'either' will always be paired with 'or'. 'Neither' is correct here, because when we replace the word with 'either', the meaning of the sentence is ambiguous. ('Either' refers to a choice that must be taken here, these qualities cannot be 'chosen' in this context.)
The correction is 'nor capable'. (I have found that he is neither willing nor capable.)
Hence option C is the correct option with the error.
The other parts (a) and (b) do not have any error in them. They are grammatically correct and are complete in meaning.
Hence options A and B are not the right answers.
Option D is incorrect because the sentence has an error (c).