The year 1848 was the one ____________ witnessed the beginning of California Gold Rush: the gold was first discovered at Sutter's Mill, in Coloma, California.
A、 when
B、 where
C、 that
D、 /
【正确答案】：C
【题目解析】：该题考查的是关系词的用法。此句中关系词作分句的主语，在限制性关系分句中关系词作主语时不能省略，when和where是关系副词不可以在分句中作主语。
