下颌中切牙牙根中部横切面形态是（）。
A.圆三角形
B.窄长形
C.卵圆三角形
D.葫芦形
E.方形
参考答案：D
The policeman________the children to cross the road when the traffic lights turned green. [ ]
A. let
B. made
C. signaled
D. called
如何评价干燥基准的优劣？
