从A、B、C、D四个选项中，选出可以填入空白处的最佳选项。
21. Of the two brothers, Bill is _______ younger one, and he is a quiet boy, ________ that most adults like very much.
A. a, one B. a, the one C. the, one D. the, the one
22. He told us sadly that more than one person in the case.
A. involved B. had involved C. was involved D. were involved
