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【单选题】
In Para. 9, what happend to hutong in most of Old Beijing at the turn of the century?A.
Large numbers of hutong of old Beijing were pulled down and few sections of the city were protected.
B.
Developpers sold few of old Beijing and many sections of the city were protected.
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【简答题】一个新类从已存在的类那里获得该类已有的特性叫作类的 ,已存在的类叫作 ,也叫作基类,产生的新类叫作 或派生类。
【简答题】纵波(P波)也叫作( ),横波(S波)也叫作 ( )。
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