m+n=n+m运用了加法结合律．______．（判断对错）
m+n=n+m运用了加法交换律；
故答案为：×．
She felt sorry that she had disturbed the __________ calmness of a man she respected.[ ]
A. regular
B. curious
C. usual
D. various
对于触电人的救护首先要（）。
A.切断电源
B.把人拉开
C.把线拉开
D.对人泼水
