It was March 14thXi Jin ping was elected chairman of the People’s Republic of ChinaA.

问题补充：

It was March 14th．Xi Jin ping was elected chairman of the People’s Republic of China

A. in which

B. that

C. until

D. when

答案：

A. in which

B. that

C. until

(答案→)D. when

解析：考查定语从句。句中先行词为March 14th．，在从句中作时间状语，故用关系副词when，或者用on which。句意：在3月14日，习近平当选为中华人民共和国主席。故D正确。