– What makes you so upset, Mr. Wang?

– That John, a student in my class, ______ himself to computer games.

A．withdraws

B．undertakes

C．conveys

D．abandons

口服液剂在贮存中常见的变质现象是

A．挥发
B．霉变
C．沉淀
D．虫蛀
E．酸败