考点二 their等物主代词
1．物主代词是常见的名词限定词, 其后既可接可数名词的单复数(his pen, his pens)又可接不可数名词(his time), 但不可与其他的限定词同时出现(部分数词除外)， 例如：不能说no my car, my no car，但是可以说 My two red cars
2．英语中许多习惯用法在表示特指时都用物主代词而不用the, 为的是更突出所属关系，这在TOEFL中是一个常考的点
例如：Manufacutrers of consumer goods often change the styles of their products.
这里用their 而不用 the
例题:
(1)
A good exercise program helps teach people to avoid the habits that might shorten the lives.
应改为: their
解释: 定冠词the指代不清, 用物主代词their作名词lives的限定语更符合英语习惯, 还可突出lives 与people之间的所属关系
(2)
A liquid is similar to a gas because has molecules are not fixed to each other in any specific way.
应改为: its
解释: has是动词, 不能修饰名词, 且与从句的谓语冲突, 依句意改为物主代词its作molecules的限定语
考点三 只接复数名词的限定词
a (large /small /great /considerable /remarkable) number of, a variety of, a set of, a few, 等表示数的固定词组之后总是接复数名词
例题:
(1)
In mathematical terms, modern algebra is set of objects with rules for connecting or relating those objects.
应改为: is a set
解释: a set of是固定词组, 表示一套、一组, 后面接可数名词的复数, 与题中objects吻合
(2)
At birth, an infant exhibits a remarkable number of motor response.
应改为: responses
解释: 短语a number of 后面要求接可数名词的复数, number前可加某些形容词如great, considerable, remarkable, small 等表示a lot of 或 a few
注意 “the number of” 和 “a number of”的区别
The number of boys in Class Five is 25. (五班男孩的数目是25，后面谓语动词用单数)
A small number of families are able to afford an apartment. (少数家庭能够买得起一套住房, )