牙冠的斜面是指（）
A.组成嵴的各个面
B.组成牙尖的各个面
C.构成轴嵴的各个面
D.构成边缘嵴的各个面
E.牙冠上斜行的面
参考答案：B
Nancy hasn’t begun on her PH.D ________ working on her master’s degree.
A. still because she is yet
B yet as a result she is still
C yet because she is still
D still while she is already
We had to wait half an hour _______ we already booked a table.
A．since
B．although
C．until
D．before
