难道不是用每段的差除以10就可以算出rate了吗。。。？

条件一的意思是X镇中的2500人中balabala，不是说X镇有2500人。

我的算法是80/250+30/250+90/250=4/5

C/D：考平行。do sth by …，rather than by…，and do sth during the day，rather than at night。
R：sb do sth by doing sth; W: sb do sth by sth；R:sb/sth was done by sb/sth，例外：i studied by candlelight

A was determined by B.表示原因，A was a result of B表示原因，二者在一起是fatal redundant。

根据绝对确定的点进行排出。

I get mail from cities as far away as New York. 我从像纽约那么远的城市收到一封邮件。强调形容词far
I get mail from cities that are as far away as New York.我从和纽约一样远的城市（都是xx公里远）收到一封邮件。that are在说明先行词的性质，和……一样远的先行词。

but连接同等级；分析句意，从而选择正确的语法。

to address the difficulties，解决难题；address the problem，解决问题

1、grow已经表达了“长大”的概念，不用再加介词up to，只需用to即可。
2、由于动词spread的单复数不同，所以其修饰的对象不同，主语也就有区别。在(A)(C)中，spread的主语为a buttressed trunk and a crown；在(B)(D)(E)中，其主语为a crown。
只有crown才能 spreads （树冠挡着别的树），而树干不可→spread不对

一步步定位；上下级表达。

C，for doing不表示目的；that离先行词effects隔了effect的定语和谓语动词are，错误；
E，what多余，语言习惯是to investigate X 而不是 to investigate what X is。
to investigate the effect而不是 to investigate what the effect is
to investigate whether global warming will occur and what impact it will have, 这里因为要与whether平行，所以用what impacts最佳

考察句子成分，单独的句子不能做主语；IT做形式主语指代整个句子；sb is more likely to do sth.

应该是 was aimed at比 was aimed to 表意更准确

whether/or的平行：
如果whether/or表示要么/要么，则whether和or各自连接的内容要平行；如果whether/or表示是否/或者是否，则or作为并列连词可以省略内容，只要有内容与or接的内容平行就可以。
R: Taiwan will whether develop a closer relationship with mainland China or preserve the status quo, depending on the will of the USA.
R: Whether Taiwan develops a closer relationship with mainland China or preserves the status quo will affect the USA.

例题1的状语从句还原的话，不是“while increasing demand rob the oysters there of their flavors and make them smaller, the increasing demand could alter the saline content of A Bay”吗，那原句也是怪怪的？还是还原得有错？

个人认为这个题目里面有一个隐含一个常识性assumption：商务舱的利润比经济舱的利润高。所以如果乘客从商务舱转到经济舱，航空公司会损失利润

because是从属连词，therefore是副词，语法上可以，但语意冗余。