介宾短语
介词不能单独使用，而必须和其他词连用，这些词称作介词的宾语，它们共同构成的介宾短语常在句中作状语，作名词的后置定语，有时作某些动词的宾语补足语
考点一 名词作介词宾语
大部分介词的宾语都是由名词(包括代词)充当的，如：under the tree, during the day, 这一考点在题中多次出现
例题：
(1)
The development of mechanical timepieces spurred the search for ----with which to regulate them.
(A) more accurate than sundials
(B) more accurate sundials
(C) sundials more accurately
(D) more accurately than sundials
答案：B
解释：search for缺少宾语, 只有B是表达无误的名词词组, 可以作宾语；其他选项的比较形式都有错。
(2)
Different species of octopuses may measure anywhere from two inches to over thirty feet in long.
应改为：in length.
解释：long 是形容词, 不能单独接在介词之后, 其名词形式length与in构成介宾短语, 表示长度
考点二 动名词作介词宾语
名词作宾语时，之后不能再接宾语，这一缺陷可由动名词弥补。
如：before doing the job , after getting back
改错题中常把应该用动名词作宾语的地方误用为名词或不定式，需留心陷阱
例题：
(1)
The Conestoga wagon, used for to carry heavy loads over long distances, originatedaround 1725 in a region of Pennsylvania occupied by the Conestoga Indians.
应改为：carrying.
解释：不定式不能作for的宾语, 改为动名词即可
(2)
Copper sulfate, spread in judicious amounts, kills algae ----harming fish or aquatic invert-ebrates.
(A) does not
(B) but does no
(C) except
(D) without
答案：D
解释：harming 是动名词形式, 因此要求前面的词是介词或可接动名词的动词. A B 可首先排除; C 虽是介词, 但与句意不符.
(3) Mary Ann Hardy was known for her skill to paint miniature watercolor portraits on ivory.
应改为：in painting
解释：后置定语修饰名词，什么方面的技能，不能用不定式。