道路主要受汽车荷载的反复作用和经受各种自然因素影响,路基、( )是道路工程的主要组成部分。
A.基层
B.面层
C.路面
D.垫层
参考答案:C
________ he finished writing his paper in such a short time surprised us all.
A.When
B.Why
C.That
D.What
汀步石既是(),又是点式渡桥。