绝经后补充雌激素可以预防骨质疏松的理由是 （） A.减少骨吸收 B.刺激骨形成增加

     Most international students are between the ages of 16 and 20 or even o  1  . These are the r  2   

ages for young people to look after themselves. International students will f  3  two problems:

independence (独立) and study.

      Firstly, It's very important for international students to have independence. If they always ask for

help from their p 4   , They will be a 5   most of the time when they study aboard.

      Secondly, international students study h  6   than they do at home. They not only study more

d 7   subjects but also have to study a f  8   language to understand their teachers and the b 9   which

they use.

      So it's not e 10  to study abroad. They must overcome (克服) the two problems if they study

aboard.

三尖瓣复合体

下图反映的是从远古到现在我国野象分布界限由北向南推移的情况，围绕这幅图文科班同学展开了热烈的讨论，下列观点正确的是

①除了气候因素外，传统农业和近现代工业的发展不可避免地影响到野生动物的分布

②野生动物的存在根本不会对人类社会构成威胁，人类对野生动物的杀戮完全出于自私和愚蠢

③野生动物在历史上是一种资源性动物，由此 形成了一些手工业，随着野生动物的消失，这些产业也随之崩溃 

④只有人类社会经济文化发展达到一定高度，保护野生动物才能真正实现

A、①②③④

B、①③④

C、①②④

D、②③④

试述利用昆虫病毒防治虫害的优缺点。

每一个商品分类层级只能采用一个分类标志。