材料老化易导致其脆性提高、强度降低，使护坡表面易呈现（）。
A.机械破碎
B.平整光滑
C.磨蚀麻面
D.粉末化破碎或层层脱落
参考答案：D
— Tom hasn't turned up yet. He might have got lost.
— No, he ________. His car has got a GPS.[ ]
A. must not have got lost
B. wouldn't have got lost
C. can't have got lost
D. shouldn't have got lost
资本市场是指期限超过一年的资金交易市场，其中（）是资本市场工具。
A.ADR
B.公司债券
C.股票
D.国库券
ave got lost