水在垂直管内由上向下流动,相距l的两个断面间,测压管水头差为h。如图所示。则两个断面间沿程水头损失为()。
A.h
B.l-h
C.l+h
D.h-l
参考答案:A
在九年级体育中考中,某校某班参加仰卧起坐测试的一组女生(每组 8人)测试成绩如下(单位:次/分):44,45,42,48,46,47,45. 则这组数据的极差为 [ ]
A. 2
B. 4
C. 6
D. 8
When asked about the secret of his success, he ______ it to his friends’help.
A.belonged
B.donated
C.owed
D.gave