(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.
A B C D
分析：D错，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
A B
starred in stage, television, and film productions on
C
both sides the Atlantic Ocean.
D
分析：D错，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
A B
can be performed from a justice of the peace. 治安法官
C D
分析：D错，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
A
could veto a declaration of war at refusing to
B C D
supply moccasins and field rations.
分析：D错，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
A
operations on sets of numbers or other elements
B C
that are often represented at symbols.
D
分析：D错，应改为by。动作的发出者应该用介词by来引导。