山谷线和山脊线是构成地貌的骨架称（）。
A.等高线
B.地性线
C.轮廓线
D.铅垂线
参考答案：B
— Daddy, would you buy me an ipod if I do well in this monthly exam?
— I ________, I promise.[ ]
A. will
B. shall
C. do
D. would
