英语学习的过程中，大家认为最难的就是语法部分。介词是考试中出现的比较多的一个部分，而其中考的最多的就是介词的固定搭配问题。
(一) 介词搭配
例：The teeth in the upper jaw function together those in the lower jaw to cut, tear, and grind food.
分析：和…一起，所以together in应该为together with，
例：The Allegheny Mountain range is rich of coal.
分析：be rich of 改为be rich in
例：The rotation of the Earth on its axis is responsible to the alternation of periods of light and darkness.
分析：responsible to 应改为responsible for。形容词responsible后接名词作宾语时要加介词for。
(二) 最重要的两个介词
1、介词of 多余或者遗漏
例：Mosquitoes usually lay eggs, singly or in batches, on top stagnant water.
分析：on top 应改为top of stagnant。on top of …是因定表达法，意为“在…上面”。
例：Christopher Plummer is a Canadian actor who has starred in stage, television, and film productions on both sides the Atlantic Ocean.
分析：sides the 应改为sides of the。 sides为名词，the Atlantic Ocean也是名词，中间明显少了一个介词。
2、介词by
一种情况表示被动，be+过去分词+by
另一种表示通过……的方式， by doing
例：The ceremony of marriage in the United States can be performed from a justice of the peace.
分析：performed from 应改为performed by。谓语动词是被动式，performed的动作执行者应该由介词by来引导。
例：Along the east coast ,American Indian women's councils could veto a declaration of war at refusing to supply moccasins and field rations.
分析：refusing to 应改为by refusing。通过拒绝提供鞋子和粮食，表示通过某种方式做某事要用介词by,故将at refusing 改为by refusing。
例：Algebra is the branch of mathematics concerned with operations on sets of numbers or other elements that are often represented at symbols.
分析：at应改为by。动作的发出者应该用介词by来引导
以上就是小编给大家分享的四级考点，希望可以给大家在备考的时候带来帮助。