Today’s young people can’t live without smart phones. They keep their hands on the phones whenever they go, even while they_______meals.

A．had

B．will have

C．are having

D．were having

关于生物膜不正确的描述是（）。

A.所有生物膜的厚度都基本相同

B.同一细胞不同部位的膜厚度不同

C.不同细胞的膜厚度不同

D.同一细胞器不同膜层厚度不同