柠檬脾气主语若相同，可省，但助动词不能省。如：
As a result of the continuing decline in the birth rate, fewer people will enter the labor
force in the 1980’s than (people省略) did in the 1960’s and 1970’s, a twenty-year period during which people born after the war swelled the ranks of workers.
(2) 介宾比较 A do sth of C1 by D1 than of C2 by D2.（C1C2，D1D2对等名词）
注意一定要是介宾才能直接跟在than后面
The clothes inside the store looked more appealing than outside the racks.错 对
(3) 宾语比较 A do C1 than C2.(C1C2为对等名词)
(4) 状语比较A do sth than usual/ever before/people expected(直接加状语)
2．一种句型只有主谓，没有宾语的句子，因为没有宾语，只可能有主语比较，因而不需要重复do来确认这是一个可发出动作的主语，所以其比较形式如下：
I eat faster than you.注意与下句区别 I eat apple faster than you do
（区分出you是主语，后面有谓语do，而不是宾语）如果写成 I eat apple faster than you 按ETS的理解，从语法上就变成我吃苹果比吃你快，成了宾语比较。逻辑上显然不通。
3．AS 族的比较大同小异，as 可单独引导比较，也可以复合成as many as, as hard as 等形式，但ETS宗旨不变，如
Sand road costs twice as many to build as to maintain(类似于介宾比较）
Sand road costs twice as many to build as stone road do(主语比较）
Sand road costs the government twice as many to build as the residents.(宾语比较)
as much/many as… 和…差不多
not so much… as… 与其说是。。。不如说是。。。
