车皮的易损部件，主要有（）等。
A.闸瓦；
B.千子；
C.弹簧；
D.手轮
参考答案：A, B, C, D
Mr Black be at home because she called me from England just now.
A．mustn't
B．isn't able to
C．can't
D．may not
receptor-mediated endocytosis (受体介导的内吞作用)
