问题补充：
Rock-climbing is a breathtaking activity, very popular nationwide among young people,
cooperation as well as courage plays an important role.
A. who
B. which
C. that
D. where
答案：
A. who
B. which
C. that
(答案→)D. where
解析：考查定语从句。本题的先行词是rock-climbing,短语从句cooperation as well as courage plays an important role的结构非常完整，所以使用关系副词where=in which。
