下列几种单一净化水的方法中，得到的水纯度最高的是（ ）

甲：连接AC，作AC的垂直平分线MN分别交AD，AC，BC于M，O，N，连接AN，CM，则四边形ANCM是菱形．

乙：分别作∠A，∠B的平分线AE，BF，分别交BC，AD于E，F，连接EF，则四边形ABEF是菱形．

根据两人的作法可判断（   ）

阅读下面短文，将短文中画线部分的句子翻译成中文
                                                                                How Much Water Is Needed a Day?
   Many people think they should drink eight glasses of water a day．Why? Because that is what they have been told all their life．But a new report on science gives some different suggestions：people should drink according to their bodies．____ They should drink as much water as they would like to drink．
   The report says most people meet their daily needs for water by letting thirst be their guide．It also gives people some good suggestions：women should get about 2.7 liters（升）of water every day，while men should get about 3.7 liters．
   There is an important difference．____ The report doesn’t tell people how many glasses of water to drink．Instead，the experts say it may not be possible to know how many glasses people really need．This is because the daily want of water can include the water in foods．

实验探究：

为了探究“甲状腺激素对蝌蚪生长发育的影响”，某校生物兴趣小组的同学设计了如下实验：

①用两只塑料水槽分别装有等量的自来水，设为甲、乙两组；

②分别在甲、乙两个水槽中放入10只生长状况不同的蝌蚪；

③在甲水槽中加入适量的甲状腺激素，乙水槽不加；

④给蝌蚪定时定量喂饲料，并进行观察和记录．