从每小题A、B、C、D中选出一个能填入句中空白处的最佳答案。
( ) 16. Cartoons are very ________, so I am very _______ in them.
A. interested, interesting B. interesting, interested
C. interested, interested D. interesting, interesting
( ) 17. Sam ______ coins since he was eleven years old, and now he has hundreds of them.
A. collected B. had collected C. has been collecting D. had been collecting
( ) 18. They are singing to _______ money for poor children in rural areas.
A. have B. raise C. take D. collect
( ) 19. Sally has been swimming ______ four hours.
A. for about B. since C. about D. /
