质膜具有()透性,其主要功能是()
参考答案:选择;控制细胞与外界环境的物质交换
Last summer, I went back to my hometown, the neighbors and the houses that I used to be familiar with were gone.
A.only finding
B.only to find
C.to find
D.found
刮削修复导轨时,其基准面应选择不可调的装配孔或()作为基准。
A.不磨损的平面
B.导轨中心
C.任意