Read each sentence to find out whether there is any grammatical mistake/error in it. The error if any will be in one part of the sentence. Mark the number of the part with error as your answer. If there is 'No error' market(d).
`("He came to report that the work went very slowly")/a` `("because the X-ray machine was not working very good")/b` `("that morning.")/c` `("No error")/d`.

Explanation

(b) Replace .very good. by .well.