Our monitor, who by then ______ admission to Fudan University, decided to do some part-time jobs to gain more practical experience.

A．gained

B．was gaining

C．has gained

D．had gained

关于化学试剂的购买下列说法不正确的是（）。

A.根据用量确定购买试剂量

B.根据应用目的确定购买试剂级别

C.易氧化及变质的试剂尽量少买

D.标准物质包装小，稳定性高可以多买