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

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.
1. Mumps are a very common disease which usually affects children.
A. are. B. usually. C. common disease. D. which
22. Children who's parents spend time with them and take an interest in their education tend to do better in school.
A. with them. B. who's. C. an interest. D. to do