丹霞地貌又称红层地貌，是指在巨厚的红色沙砾岩上发育的（）等特殊地貌。
A.方山
B.奇峰
C.岩洞
D.赤壁
参考答案：A, B, C, D
准线方程为x=2的抛物线的标准方程是
A．y2=-4x
B．y2=-8x
C．y2=8x
D．y2=4x
The dog may be a good companion for the old. _______, the need to take it for walks may be a disadvantage.
A．Besides.
B．However
C．Therefore
D．Instead.
