复合树脂充填时，不宜用氧化锌丁香油糊剂垫底是因为（）

A.可致树脂性质改变

B.影响树脂聚合

C.影响树脂与牙粘接

D.抗压强度不足

E.使树脂色泽改变

The volunteers try to convince people _____ the fact that some species are in danger of _____.

A．for; dying away

B．about; dying down

C．of; dying out

D．on; dying off