Some of the sentences are grammatically correct and some are incorrect. Find out which part of the sentence has an error and mark that part. If there is no error , mark that part as your answer.
`("The train is supposed")/a` `("to arrive at 10 a.m. yesterday")/b` `("but it was an hour late")/c` `("No error")/d`

Explanation

(a) Say .was supposed.