如图是表示气体分子的示意图，图中

和

分别表示两种不同质子数的原子．

属于纯净物的有______属于混合物的有______．

If Becky hadn't missed the bus, she ______late for the lecture.[      ]

A. would have been          

B. wouldn't have been

C. had been                  

D. wasn't