返回一个由字符表达式的第1个字符重复组成的指定长度为数值表达式值的字符串的函数为
A) Space B) StriogC) Left D) Right
参考答案:B
You can go and play games with your friends when you finish your homework. But remember all the
lights when you leave. [ ]
A. to switch off
B. to switch on
C. switching off
D. switching on
三相电源的连接方式为三角型和星型。