离子利用ATP逆浓度梯度过膜转运的方式是（）

A、被动转运

B、促进扩散

C、内吞作用

D、主动运转

E、胞吐作用

Being physically examined for free twice a year is what every clerk _____ be ensured in any company of the

state.[ ]

A. must

B. shall

C. ought to

D. need