【单选题】三相全控桥式整流电路电感性负载无续流管,控制角α大于( )时,输出出现负压。 A.90° B.60° C.45° D.30°
【单选题】What is people's attention turning to today according to the passage?
A.
The causes of traffic accidents.
【判断题】ABO血型不合的输血反应属于Ⅱ型超敏反应。( )
【单选题】Rh血型不合的输血反应属于哪一种超敏反应( )
【单选题】The mainly idea of this passage is ______ .