关于比较题中的几个问题！（我知道发在这里不对，但是要考了真的很急，大家帮忙看一下吧！）

一、there be
曼哈顿语法中，好像说过，there be比较时不能省略第二个there be，我想知道这条原则到底适用不适用呢？因为找到几个反例：
e.g. ...there are much larger populations of pesticide-degrading microbes in soils that are free of sth. than in soils with sth.
eg. ...there are more babies by women over 30 years old than under it.
下面的两个例子，there be都没有省略：
eg. There are about as many gym members in the boxing class as there are in the aerobics class.
e.g. There is now one microcomputer for every 32 pupils, four times as many as there were 4 years ago.


二、比较中有一种固定搭配，是than anticipated或者than estimated，我想知道的是，如果主句本身是过去时，那么估计和预测应该是过去的过去，用不用变成than had been anticipated或者than had been estimated？还是说，不用考虑时态？


三、白勇语法中说，当比较从句中的主语和谓语与主句的主语和谓语相同时可以全部省略，保留作状语的介词短语或状语从句。我有一个疑问，这里的谓语相同到底是指什么，时态如果不一样还算做谓语相同吗？比如，主句中是is，从句中是was。还有主句中是would have to do，从句中是do。
e.g. Demographers would have to konw a great deal more than they do now about the social and economic determinants of fertility. 这句话中，主句是would have to，从句是do，连个谓语是不一样的吗？抓狂TAT

...there are more babies by women over 30 years old than under it.
为什么不能看成是30岁以上妇女生的宝宝多于30岁以下妇女生的宝宝呢？这样还是宝宝比较啊……
There are about as many gym members in the boxing class as there are in the aerobics class.
这句话中，如果看成是in the boxing class和in the aerobics class比较，如你所说，there are也是不需要的啊，但是还是没有省……