某同学静止站在磅秤上,在下列几对力中,哪一对是平衡力( )
根据问句选答句。
How old are you?____ A. I'm 10.
Happy birthday!____ B. Five.
How are you?____ C. Thank you.
How many boxes?____ D. I'm fine, thank you.
I have a ruler.____ E. Me, too.
若宇航员被困火星,物质补给至少要四年才能到达,如何坚持下去?北美票房《火星救援》告诉你被困的马克如何解决影响生命的四大问题!