蜗杆传动的主平面是____平面。
A、垂直于蜗杆轴线并通过蜗轮轴线
B、垂直于蜗轮轴线并通过蜗杆轴线
C、蜗杆的端面
D、蜗轮的端面

A．反相比例运算电路
B．同相比例运算电路
C．积分运算电路
D．微分运算电路

A．Jane’s situation changed for the better while that of Rochester changed for the worse.
B．Both Jane and Rochester started to realize the importance of religion in their lives.
C．Jane became gentler, understanding and patient, while Rochester became more bad-tempered.
D．Jane became more beautiful while Rochester lost his sight, hearing and the use of a hand.

A．甲构成放火罪
B．甲是放火罪的未遂
C．甲是放火罪的既遂
D．甲不构成犯罪