It was on July 1, 2006 Qinghai-Tibet railway began operation, is a symbolic project in China’s West Development Strategy．
A. when; that
B. that; when
C. which; when
D. that; which
网友回答
A. when; that
B. that; when
C. which; when
(答案→)D. that; which
解析：第一个空是强调句型，因此填that；第二个空是由which引导的非限制性定语从句。故选D。