段修时,货车制动梁端轴磨耗超过()时,应进行焊修。
A.2mm
B.2.5mm
C.3mm
D.3.5mm
参考答案:C
— Would you like to play bridge with us?
— Sorry.___________. [ ]
A. With pleasure
B. No problem
C. It isn't my cup of tea
D. It is a piece of cake
某人造卫星运动的轨道可近似看作是以地心为中心的圆.由于阻力作用,人造卫星到地心的距离从r1慢慢变到r2,用El、E2分别表示卫星在这两个轨道上的机械能,则( )
A.r1<r2,E1<E2
B.r1>r2,E1<E2
C.r1>r2,E1>E2
D.r1<r2,E1>E2