A:must come
B:would come
C:must have come
D:would have come
如图,点E在DA的延长线上,下列条件中能判定AB∥CD的是( )
若﹣2x3m+1y2n与4xn﹣6y﹣3﹣m的积与﹣x4y是同类项,求m、n.
①稀醋酸;②浓硫酸;③稀硝酸至恰好完全反应,并将上述过程中放出的热量分别记为Ql、Q2、Q3.
下列关系式中正确的是( )