— Margaret ________ stay at home all day long in front of the computer.

— That's right. She should go to the fitness center with us. [    ]

A. doesn't have to  

B. couldn't

C. oughtn't to  

D. may not

靶心率一般取最大心率的（）

A.40%～55%

B.50%～65%

C.60%～75%

D.70%～85%

E.80%～95%