单选题 The day ______ I shall never forget is the one ______ I joined the army.
A. that...where B. when...in which
C. which...when D. on which...why

【正确答案】 C

【答案解析】“I should never forget”和“I joined the army”都是定语从句。选择引导定语从句的关联词要看先行词在定语从句中作什么成分。先行词day在其后的定语从句中作。forget的宾语，所以要用关系代词引导。而因为在定语从句“I joined the army”中，主语和宾语都有，是完整的主谓结构的句型，所以the one在其后的定语从句中只能作状语，这样就要用关系副词来引导，所以使用when。