防爆结合面的长度由（）决定，一般有6.0、12.5、25、40mm等几种尺寸。
A.外壳
B.隔爆外壳
C.隔爆外壳的容积
D.光洁度
参考答案：C
In fact most people in that area are _______ than they were 5 years ago because of years of wars.[ ]
A. poorer off
B. worse off
C. better off
D. richer off
电磁系仪表为什么应用广泛？修理时应注意哪些问题？
