问题
选择题
In face of the challenge for the moment, it's most important to ________ a good state of health. [ ]
A. keep up
B. keep away
C. keep off
D. keep out
答案
答案：A
搜题请搜索小程序“爱下问搜题”
In face of the challenge for the moment, it's most important to ________ a good state of health. [ ]
A. keep up
B. keep away
C. keep off
D. keep out
答案：A
周期中，前面的
被截去，从而改变了电灯上的电压。那么现在电灯上的电压为
