问题补充:
China’s reform and opening up in late 1978, its quick development has aroused worldwide attention, which has made America anxious about it.
A. When
B. As
C. While
D. Since
答案:
A. When
B. As
C. While
(答案→)D. Since
解析: since引导一个时间状语从句,或接一个短语时主句要用现在完成时。