避雷线在防雷保护中所起的作用是（）。
A、防感应雷
B、防高压雷电波
C、防直击雷
D、防内部过电压
参考答案：C
The book is _______ that one.
A．as three times long as
B．three times the length of
C．three time as long as
D．three times as longer as
