问题补充：
At school we take exercise for an hour every day to build us up.
A. cheer us up
B. make us happy
C. change us
D. make us stronger
答案：
A. cheer us up
B. make us happy
C. change us
(答案→)D. make us stronger
解析：句意：在学校我们每天锻炼一小时来强壮身体。Build up加强；A使我们振作；B让我们高兴；C改变我们；D让我们更强壮；故D符合题意。
