单项选择题双向晶闸管在( )象限有对称的伏安特性。 A. Ⅰ和II B. Ⅰ和Ⅲ C. Ⅰ和IV D. II和IV
单项选择题She’s always been kind to me –I can’t just turn ______on her now that she needs my help.A.my back B.my head C.my eye D.shoulder