-- Could you tell me __________ yesterday?
-- Because my bike was broken on my way here.
A:why you came late
B:why do you come late
C:why you come late
D:why did you come late
计算(﹣a)3•(a2)3•(﹣a)2的结果正确的是( )
处于基态的氢原子吸收一个光子后,则下列说法错误的是( )
若x,y满足约束条件 {x−y≥0x+y−2≤0y≥0 ,则z=3x﹣4y的最小值为____