Some of the following sentences are grammatically correct and 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.
`("For a long time")/a` I did not know `("who")/b` was sitting `("besides me")/c` because `("it was very dark.")/d` `("No error")/e`

Explanation

(c) Use .beside.