历年
1. 主系表/主谓宾结构中主语和表语/宾语数量不对等
首先我们要弄清主系表结构的含义。英文中主系表结构由主语，系动词和表语组成。主语为名词或者代词，位于句首。表语用来修饰主语，说明主语的身份、性质、品性、特征和状态，位于系动词之后。通常由名词、形容词、副词、介词短语、不定式、动词-ing或者从句来充当。例如：
He is at home. (at home是介词短语，作表语)
My favorite subject is reading. (reading是动名词，作表语)
系动词分为三类，
-Be动词
-表感官，如
Look, feel, seem, smell, taste, sound, touch
-表状态维持或转换，如
Turn, get, go, fall, remain, become, prove, appear, keep, stay, continue, stand
总而言之，系动词和表语联系十分紧密，有系动词就有表语，有表语就有系动词。在这一类考点中，形式多呈现为一个变多个或者多个变一个。
2009.10
(A significant factor )to include in the budget when (buying a car are the costs of fuel and maintenance and the( insurance payments.)
解析：每一道IE题，最重要的都是划分句子主干，先阅读句子的主干成分，即A factor are costs.很明显，这句话的主语是单数，而表语是复数，应把A改为Significant factors.
2010.1
A big vegetable salad is( generally )more nutritious (than )a low-fat pasta dish, (but )either meal would be (good choices) for the health-conscious eater.
解析：这句话主干是A salad is more nutritious than a dish, but either meal would be good choices. 问题在于后半句would be系动词连接的两部分数量不一致。
IS中也有同样的考点：
2009.5
Turquoise-inlaid frog and bird figurines( seems to have played an important role )in prehistoric ceremonies in what is now the southwestern United States.
(A) seems to have played an important role
(B) seems to have played important roles
(C) seems to be playing an important role
(D) seem to have played played important roles
(E) seeming to be playing important roles
解析：seems to have played是复合谓语，主语是复数，根据主谓一致必须用seem，且不可能是一个role，因此选D.
2011.1
Although Debussy and Ravel are generally considered( an impressionist composer, their compositional styles are) quite distinct from one another.
(A) an impressionist composer, their compositional styles are
(B) to be an impressionist composer, their compositional style is
(C) as having been impressionist composers, their compositional style is
(D) impressionist composers, their compositional styles are
(E) impressionist composers, whose compositional styles are
解析：Debussy和Ravel不能被看作一个人，排除A,B. 而C答案中style是单数，两个人的风格是styles;根据although的连词性质，后半部分必须有完整的句子，所以E的whose错。选D。
2. 介宾短语中宾语数量错误
介宾短语=介词+宾语，这个成分可以用来作定语，状语，表语和补语。在IE中多以as...作补足语形式出现，as后面所接名词的数量与前文不符。
2009.5
In the early twentieth century, telephone companies (supported) the (cause of) financial independence for woman (by providing )many with respectable jobs as (a switchboard operator).
解析：时间状语是20世纪早期，因此supported时态正确，短语cause of...和support...by doing正确，最后一个选项中as...介词短语作宾补，因此需要和jobs数量一致。答案D。
2009.10
Throughout the season he coach (would often )remind us that the best teammates are not those who strive to set individual records (but those )who fit in as (a member )of a cohesive unit.
解析：这里B,C答案中的but those和not those平行，所以排除，would often时态正确，A排除，而fit in as a member中as a member是介宾短语作补足语，因此宾语在数量上必须和主语who一致，故改成as members.
IS考过介词from后面接宾语数量错误的形式：#p#分页标题#e#
2007/10
Those enrolled in the leadership training courses have evolved into dynamic, confident managers,( from an inexperienced and uncertain newcomer )just a month ago.
(A) from an inexperienced and uncertain newcomer
(B) from the inexperienced and uncertain newcomers they were
(C) from being inexperienced and uncertain newcomers
(D) instead of the inexperienced and uncertain newcomers of
(E) after being an inexperienced and uncertain newcomer
答案：B
2009.1
The second-year students at this college have evolved into insightful, critical thinkers( from an inexperienced and uncertain teenager just a year before).
(A) from an inexperienced and uncertain teenager just a year before
(B) from the inexperienced and uncertain teenagers they were just a year ago
(C) even though just a year before they were an inexperienced and uncertain teenager
(D) in just a year from an inexperienced and uncertain teenager
(E) when in just a ear they were inexperienced and uncertain teenagers
答案：B
这两题用了同一个短语Sb. evolves/evolve from A to B，在这个句型里A和B需要数量一致。
3.列举项的数量与提示词数量不一致
多在列举事例的时候出现，例如such as..., include...等等，
2009.5
Cinco de Mayo, or May 5, the date of a famous military victory, is celebrated (with such an activity as )dancing, parades, musical performances, and feasts.
(A) with such an activity as
(B) with an activity such as
(C) with such activities as
(D) in such activities like
(E) in an activity like that of
解析：such as是固定搭配，排除D，后面列举了四项活动，前面却用了an activity，排除A,B,E，所以选C
2010.5
(Many of )the senator’s speeches, which were( enthusiastically received )by the large crowds (that )came to see him, addressed (an important topic), including health care and global warming.
解析：including后面列举了两个话题，和an important topic矛盾，所以选D。
这两道题关键词都在错误部分后面出现，需要尤其小心。
4. Their+名词，名词数量错误
一般来讲，their后面需要接复数名词，这也是常考的形式，例如：
2010.1
The people sitting behind me in the movie theater were talking throughout the film and would not keep their voice down even after being asked to do so.
解析：voice是个可数名词，需要改成voices
George Thornton Emmons( A was one )of a handful of ethnographers who (B committed )(C their life)( D to studying )the Tlingit culture of the Northwest Coast. (E No error).
解析：这道题来自OG。life表示生命的时候可数，表生活的时候不可数，而commit one’s life to doing根据句意表示生命，所以应该是their lives，答案C。
当然，并不是所有在their后面出现的名词都必须用复数，到底要不要加复数取决于这个名词可数还是不可数，或者这个名词能不能被共享。例如：
不可共享：their voices;their minds;their lives(生命)
可以共享：their life(生活);their independence