Many athletes are clear that the Olympic Games are the only time they will be watched by thousands of millions.
A. that
B. which
C. where
D. when
网友回答
A. that
B. which
C. where
(答案→)D. when
解析：D 考查定语从句。分析句子结构可知，“ they will be watched by thousands of millions”为定语从句，先行词为time，空处在从句中作时间状语，所以用关系副词when。