Read each sentence to find out whether there is any grammatical error in it. The error, if any will be in one part of the sentence. The letter of that part is the answer. If there is no error, the answer is 'E'. (Ignore the errors of punctuation, if any).
They would not have able to plan the details of the job, if you had not cooperated.
They would not
have able to plan
the details of the job,
if you had not cooperated.
No error
Correct answer is B
have been able to plan