城市人口性比
参考答案:
城市中人口总数火某个龄级的个体重男人对女人的比例
—Have you seen my pen bought during my visit to Hong Kong Disneyland?
—Oh, Jane must have taken it _________ ; she has the same one as yours.
A.by mistake
B.on purpose
C.by chance
D.by accident
岩石破坏有几种形式?对各种破坏的原因作出解释。