失血性休克是出血占全身血容量的()
A.10%
B.15%
C.20%
D.30%
E.40%
参考答案:C
解析:由各种原因造成失血超过全身总量20%,即出现休克。
用滑轮组提升重物,请在下图中画出拉力F=13G的绳子的绕法.(不计动滑轮、绳重和摩擦)
There was _____smoke that they couldn't see anything clearly. [ ]
A. too
B. too many
C. so much
D. so many