Little Bob is often educated by his parents to be good and friendly to anyone even if ________.

A．attacking

B．is attacked

C．to be attacked

D．attacked

造成转相的原因是（）。

A．Zeta电位降低

B．分散相与连续相存在密度差

C．微生物及光、热、空气等的作用

D．乳化剂失去乳化作用

E．乳化剂类型改变