手工电弧堆焊时，焊机空载电压不能太高，一般直流焊机电源的电压≤（）V。
A.60
B.80
C.100
参考答案：C
根据液体的连续性方程，液体流经同一管内的不同截面时，流经较大截面时流速较快。
—Where _____ your new pants?
—_____ on the bed. [ ]
A. is, It's
B. are, They're
C. is, They're
D. are, It's
