已知X2∑=0.388,X0∑=0.296,则单相短路时的为()。
A.0.102
B.0.688
C.0.684
D.无法知道
参考答案:C
如果a>b,那么下列不等式一定成立的是( )
A.a+c>b+c
B.c-a>c-b
C.-2a>-2b
D.a2>b2
He kept yawning in class this morning. That is _____ he stayed up late doing his homework last night.
A.why
B.how
C.because
D.whether