螺距的单位是
A.mm/rB.mmC.mm/sD.r/mmE.无量纲单位
参考答案:E
解析: Pitch=S(mm/r)/W(mm),螺距是无量纲单位。
We have to ________ school uniforms in school every day.[ ]
A. put on
B. have
C. wear
D. are in
冠心病的危险因素有()
A.TG升高
B.LDL-C升高
C.TC升高
D.HDL-C降低
E.LPA.升高