1. 主谓一致是什么
中文中，你说任何一句话，都是没有动词时态、语态、单复数变化的。
我爱他。他爱我。动词“爱”，没有任何时态、语态、单复数变化。
所以中文是很容易的对不对？对于我们中国人而言，确实如此。可对老外，学中文可是相当难的。
换作英文。I love him. He loves me. love作为动词，如果前面主语是复数，则动词必须是复数形式；如果主语是单数，那动词也得是单数形式。
目的何在？为了保证语法形式上的一致性，单数都是单数，复数都是复数。因此，英语是语法结构十分严谨的语言，通过语法形式传达出内在意义。
2. 主谓一致怎么用
很重要的一点就是，分清楚什么算复数，什么算单数。
通常是觉得，有-s结尾的单词或是名词复数，一般是复数；否则，就是单数。但实际情况并不是如此。
从根本上讲，就是看主语到底是几个。如果是一个，就是单数；如果是两个或两个以上，就是复数。
2.1 以-s结尾的单词
比如，以-s结尾的疾病名称、游戏名称、地理名称，以-ics结尾的学科名称，或者是其他以-s结尾的词，看似复数，实际上是一个东西，一个整体的东西，因此是单数。
Darts (投镖) is essentially a free and easy game.
Arthritis is a disease causing pain and swelling in the joints of the body.
Physics is an important subject in middle schools.
The United States is a country of people with varied origins.
The only means to achieve success is to appeal to arms.
2.2 集体名词
一些常用复数，比如police, people, cattle, poultry。
一些常用单数，比如machinery, equipment, furniture, merchandise。
既可以单数，也可以复数，比如audience, committee, class, crew, family, government, public。看具体情况是单数还是复数。
That group of soldiers is a top-notch fighting unit.
That group of soldiers have the best performance.
最后一种，a committee/panel/board of后都加单数，因为是一组人员，落实到单复数是一组而已。
2.3 并列结构
主要根据意义来确定单复数。不管是什么并列结构，都看主语到底算一个整体，还是看是多个当成复数。
比如Ham and eggs is a good breakfast. 强调的是一顿早餐，ham和eggs要看成一个整体。
而Ham and eggs are useful to human beings. 侧重讲两种食材，为复数。
并列结构包括and, both...and..., as much as, as well as等。
而nor, or和either...or...主要遵循就近原则。
Either her father or her mother calls for her every day.
Either her father or her brothers call for her every day.
2.4 数量概念的名词词组
all/some/none/half/most/lots/loads/plenty/分数+of词组，看名词单复数。
60% of the city was destroyed.
60% of the doctors(医生) are doctors(博士).
Some of the kids are male.
Some of the bread was not edible.
A portion/series/pile/panel/kind/sort/type + of词组，the kind/sort/type + of词组，many a/more than one+名词，后接单数，因为整体实际上是一个。
A pile of dogs was set beside the wall.
This type of car is old-fashioned.
Many a man has done this duty.
More than one game was lost.
其实核心就是看，名词数下来，个数到底是1个，还是2个或2个以上。前者是单数，后者是复数。
2.5 其他语法形式
单个名词性从句、非谓语都是单数。
名词性从句作主语表示两件事情，what引导的是复数名词，one of+复数形式+关系分句以及强调句，都要看真正的主语（到底是指代of后的还是one，被强调的内容）是单数还是复数，谓语动词才对应相应的形式。
What caused the accident is still unknown.
To eat well is all he asks.
What caused the accident and who was responsible for it remain a mystery to us.
What are often regarded important are actually the fruits and vegetables.
Joan is one of those people who go out of their way to be helpful.
He is the only one who is willing to go there.
It is me that was injured in the accident.
It is I who am a boy.
3. 一段搞定主谓一致
说来说去，就是要确定，主语，也就是动作的发出者，到底是几个。单数1个的话，就是单数。复数2个或2个以上，就是复数。
一段话，希望您能理解并借此掌握主谓一致。一般主谓一致体现在现在时中，在过去式或将来时中，主谓一致体现的就不那么明显。因此，若你要避免主谓一致中的尴尬，就多用其他时态。
An apple a day keeps the doctor away. But people haven't formed this habit. What requires to be done is actually maintaining the behavior for at least 21 days. In other words, it is discipline and persistence that is required to form a habit. For us, buying apples regularly is a good start in this regard. Even though you may not be one of those who have good self-control, you are the only one who helps yourself to achieve the goal. Therefore, just do it. 80% of the starters end up giving up their efforts. What about you?