ex. Sb is at least fifty percent less likely than those who are sedentary to die of a heart attack.
六、重要考点
1.主从句的情态可一致，也可不一致 I eat more food than he can
2.that从句和because从句形式上不对称，不能比较；动名词和不定式不能比较 （平行部分不能平行的结构均不能相互比较）
3. whereas = while（while前后句子之结构要求并列相对）
whereas连接的平行比较只要求对比的核心逻辑上有对称关系，不要求对称位置必须是对称名词
Over 75 percent of the energy produced in France derives from nuclear power, whereas nuclear power accounts for just over 33 percent of the energy produced in Germany. 主从句的主语分别是energy和nuclear power并不是对称名词，但是对比的核心都是“核能发电占总产出能量的份额”：
*但是如果whereas后面接介词短语，那么主句的开头也必须需要是介词短语(whereas后出现介词短语或者状语都会非常对称)，如果whereas后接单纯主谓宾（或主系表），主句也要尽量用单纯的主谓宾（或主系表）来对应，除非同下面GWD 18-2一样后半句主谓即已经可完全表达出“对称”的含义（each language occupies a distinct area of the brain是主谓宾齐全；language areas overlap是主谓，没有宾语。但两个分句依然算是平行，因为逻辑已经平行。）：
prep1-29 Pine trees thrive in relatively wet climates, whereas oaks prefer drier ones. prep1-54 In cooking, small quantities of spices are used, whereas in medicinal usage spices are taken in large quantities in order to treat particular maladies.
prep2-102 Whereas a female grizzly bear in the Rockies typically occupies a range of 50 to 300 square miles, a male will cover 200 to 500 and occasionally as many as 600.
GWD18-2 According to findings derived from functional magnetic resonance imaging (MRI), the area of the brain in which a second or third language is stored depends on the age of the language learner; whereas each language occupies a distinct area of the brain in an adult learner, language areas overlap in a young child.
4. like/unlike后只加名词(不一定具体名词)表比较，不能加不定式短语,分词短语(prep 1-54 unlike cooking with speices错),句子或介短。（后面接这些东西的时候unlike要改为whereas等等）。
like/unlike是严格的硬梆梆比较，比较对象必须严格对等，中间尽量不能插入任何成分（比如有一个题目是:Unlike A, in 1990 B...就算A，B可比，但这样就是不佳的表达，因为这会让读者花费脑细胞去找unlike和哪个在比。最好的句子一定是排版最严谨、最遵循规则的句子，一定是读起来最省力的句子），但是非限制性定语从句这一类非常明确是紧跟着前面的名词的修饰成分是可以的。
动词
动词时态 一、现在完成时
1.现在完成时表示的是一个行为发生在过去，但状态继续到现在，或者是仍然对现在有所影响。而一般过去时表示的一个行为发生在过去，已经结束且对现在没有影响。 2.现在完成时标志: since+时间点；for+时间段；a century of…; recent+时间短语
within/in/over/during+ the past/last/recent+时间段
二、过去完成时
1.两个行为都发生在过去，而较早的那一个要用过去完成时，通常用来强调顺序。如果句子中的时态顺序已经说明则没有必要使用过去完成时
如果主句和分句主语相同，且以 and, but, before, after 等连接，如果句子逻辑上存在先后顺序的话，主分句都用一般过去时即可。
e.g.: Antonio DROVE to the store and BOUGHT some ice cream. Laura LOCKED the deadbolt before she LEFT for work.
2.没必要一定要通过一个一般过去时的标志词来决定是否需要过去完成时。甚至可以通过时间来表示 Right: By 1945. the United States HAD BEEN at war for several years. right: By the end of the Apollo program, twelve Americans had walked on the moon. 3.若转述一个人发表的演讲或者报告（直接引语变间接引语），要将现在时转化为过去时，过去时转化为过去完成时，将来时转化为条件状态（will---would）（各退后一个时态）
在间接引语里，主句若是现在时，则从句时态必须不能早过其时态，即必须是“现在时间内的某个时态”；同样，如果主句是过去时，则从句必须时过去时间内的某个时态。（either “present + future” or “past + conditional”）。
三、将来时：
1.条件从句/时间从句/方式从句/让步从句不能用将来时或过去将来时，常用一般现在时代替一般将来时，一般过去时代替过去将来时。（对比状从省略的几种是：转折，时间，条件。） Several senior officials spoke to the press on condition that they not be named in the story （主将从现。。。）
2.possibility that?/likelihood that?/expect that?/have confidence that…中,that从句后用一般将来时
3.一般将来时一般使用will,主观将来时用be supposed to do,较少用be going to do,不用be doing/be to be done/be to do/ be going to do
四、特殊考点：
1.表示一般状态的动词不用进行时，比如know, signify（意味着），emit(发射)，die 3.continue不能用进行时态，不用两种以上的时态
4.即时动词不用完成时态：begin，discovery
5.一个句子中的不同动词时态。若在一个句子里，两个动词的时态一样，代表两个动作是平行的，同样重要的。若一个句子里两个时态不一样，则时态近的是主句，另一个动作通常代表一个背景介绍。
e.g.: She WAS PLAYING with her friends when the babysitter ARRIVED. 6.动词的时态上不能有间隔，只有相邻的时态才能出现在一个句子中 7.by the time… “到…为之” 从句一般过去时，主句过去完成时 ex. by the time I got to the station, the train had already gone. by the time “当…的时候” 句子一般过去时
by+将来时间，主句用一般将来时或者将来完成时 例句 by+过去时间，主句用过去完成时
动词语态 主动/被动 一、重要考点
by后面一般跟动作的执行者且一定是被动语态； through 和because of 后面跟一些设备手段或者方法
只有及物动词才能用被动语态 主动语态可以和被动语态平行*
二、不能用被动语态的动词
lead; cause; enable; become; receive; visit; Lack; enter; cost; possess; resemble; last; like; enjoy; notice; watch; look at; listen to; pay attention to; suit; fit; contain; so as to do; be able to do; be likely to do
三、主动形式表达被动含义
read like…/well, prove helpful, sell well (sth be sold for+price), be worth doing, require doing
动词语气 陈述语气，虚拟语气 一、if（as if/though）条件从句
时间 将来
从句谓语形式
动词过去式(be用were) should + 动词原形 were to + 动词原形
现在 过去
动词过去式(be 用 were) had +动词过去分词
would / should / might / could + 动词原形
would / should / might / could 主句谓语形式
would / should / might / could + 动词原形
have + 动词过去分词
其他形式：
But for N, S + should/would/cold/might + V / (have Vpp.) 若不是N, S应该?. = If it were not / (had not been) for N, S = Were it not for N / (Had it not been for N), S
= Without N（介词只有without可表虚拟语气）, S （为什么感觉时态怪怪的）
二、命令虚拟 v. that + do (should一定要省略) 1.命令性动词（只能用that从句的命令虚拟语气，不能用不定式）：require， demand, dictate, insist, mandate, propose, recommend, request, stipulate（规定）, suggest （*其中propose,当句子中的两个动词发起者均是一个主语时，可以用不定式。 The attorneys proposed to meet the following day.）
2.只能用不定式的动词，这些动词后面不能加宾语从句 只能用 v. sb to do sth allow, forbid, persuade, want (allow that…承认)，force, permit, prohibit
3.既可以接that从句的命令虚拟语气，又可以接不定式：ask, beg, intend, order, prefer, urge, require
4.具有命令性的词汇的名词形式同样应用虚拟语气 Right: His demand THAT he BE paid full severance was not met. 5.形容词性的命令词汇既可用虚拟语气，也可用不定式 it is + adj.+that..be../ It is +adj.+to do
adj.: advisable, crucial, desirable, fitting, imperative, important, essential, mandatory, necessary, preferable, urgent, and vital.
四、if…then 结构 then通常省略 (1)表示确定
IF Present, THEN Present.
IF Sophie EATS pizza, THEN she BECOMES ill.
This pattern is equivalent to whenever: WHENEVER Sophie EATS pizza, she BECOMES ill, (2) 表示某种程度上的不确定 IF Present, THEN Can or May.
IF Sophie EATS pizza, THEN she MAY BECOME ill.
(3) 确定-用于将来时态（现在发生的某些事情造成将来的影响）： IF Present, THEN Future.
IF Sophie EATS pizza tomorrow, THEN she WILL BECOME ill.
Another possibility for the Particular Case (in the present) is Present Perfect: I f Sophie HAS EATEN pizza, then she WILL BECOME ill. (4) 不确定-将来时态：（对现在、将来的虚拟）
IF Hypothetical Subjunctive（虚拟语气）, THEN Conditional（情态动词）. IF Sophie ATE pizza tomorrow, THEN she WOULD BECOME ill.