Even though they had been living side by side for twenty years, the two neighbors are not very friendly to each other.

A．had lived

B．have been living

C．having been lived

D．having been living

关于核孔复合体，下列描述中哪项是不正确的（）。

A.在代谢或增殖不活跃的细胞中核孔数目较多

B.核孔复合体是一种复合性结构

C.核孔复合体由内外两层核被膜融合形成

D.核孔复合体是胞质和核内物质交换的主要通道

E.广为人们接受的核孔复合体的结构模型是捕鱼笼式结构模型