问题：
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
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 |
参考答案：