摸玻璃油灰时,应比槽口()
A.高2mm
B.低2mm
C.高1mm
D.低1mm
参考答案:C
Of all the students in our class, she is ______. [ ]
A. most careful
B. careful
C. more careful
D. the most careful
我们所说的电源的效率就是电源的输出功率对输入功率的比。