Though having lived abroad for years，many Chinese still________the traditional customs.

A．perform　　　

B．possess

C．observe　　　

D．support

钼可以干扰铜的代谢，动物进入高钼草地放牧，血浆铜浓度则（）。

A.下降

B.升高

C.先升高后降低

D.先降低后升高

E.不变