前牙缺失，牙槽嵴无倒凹，观测模型时应（）
A.向后倾斜
B.向前倾斜
C.向左倾斜
D.向右倾斜
E.不倾斜、平放
参考答案：B
I could have arrived much earlier, but I ____ in the traffic.
A．would be caught
B．was caught
C．has been caught
D．had been caught
圆顶薄壳结构的组成和特点是什么？
