题目

  Tom ____ in the company since he left school in 2000 A. works         B. has worked    C. worked                D. will work 答案：B锌铜原电池产生电流时，阳离子                                   （      ）A．移向Zn极，阴离子移向CU极     B．移向CU极，阴离子移向Zn极C．和阴离子都移向Zn极           D。和阴离子都移向CU极