晶闸管整流电路中的续流二极管只是起到了及时关断晶闸管的作用，而不影响整流输出电压值和电流值。
参考答案：错
普通顶管法施工时工作坑的支撑应形成()。
A.一字撑
B.封闭式框架
C.横撑
D.竖撑
From cave paintings and from （） on bone and reindeer horn, it is known that prehistoric humans were close observers of nature who carefully tracked the seasons and times of the year.
A．apparently regular scratches
B．scratching apparently regularly
C．regular scratches apparently
D．scratches regular apparently
