Mark the letter A, B, C or D on your a...

Câu hỏi: Mark the letter A, B, C or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.
Both Mr. and Mrs. Smith are explaining the children the rules of the game.

A. both Mr. and Mrs. Smith    

B. are

C. explaining    

D. the children the rules of the game