Below a statement has been divided into five parts. The one in the bold is the fixed part in which no changes can be made. Among the other parts (A), (B), (C) and (D), find the error free parts. If the statement has no error, mark the fifth option (No error).

Sleeping are necessary (A)/ to keep us on good health(B)/ along with (C)/proper diet and (D)/ a moderate exercise regime.