— Many species are in danger of dying out because of a________of habitat.

— I couldn't agree more.We must take action for them as well as for ourselves. [ ]

A. waste  

B. possession  

C. pollution

D. lack

下列叙述不正确的是  [ ]

A．构成分子晶体的微粒中一定含有共价键

B．只含有共价键的化合物一定是共价化合物

C．离子晶体中不一定只含有离子键

D．同主族元素形成的氧化物的晶体类型可能相同