利用超导材料和科学技术可以实现磁悬浮.若磁悬浮列车的质量为20 t,因磁场间的相互作用而浮起的高度为100 mm,则该过程中磁悬浮列车增加的重力势能是( )
Miss Li,could you please help me____this math problem?
OK.Let me try.( )
A.look upB.work outC.set up
Must I wait here all morning?I have a lot of work to do.
No,you____.You may be back in the afternoon.( )
A.mustn'tB.can't
C.don't have to
Grandma is rather deaf,so you must speak clearly and___to her.( )
A.quietlyB.loudlyC.noisily
I'd like to hold our next meeting____June 23rd.Is that OK for you?( )
A.inB.atC.on
s Tom____boy in your class?
Yes.Nobody is taller than him.( )
A.the tallestB.the strongest
C.the cleverest