–Why, Jack, you look so tired!

--Well, I ___the house and I must finish the work tomorrow.

A．was painting

B．will be painting

C．have painted

D．have been painting

引起破裂的原因是（）。

A．Zeta电位降低

B．乳剂放置后出现分散相粒子上浮的现象

C．微生物及光、热、空气等的作用

D．乳化剂类型改变

E．乳化剂失去乳化作用