介詞是托福考試試題中比較活的詞性，而且具有一定的難度。中國考生一向?qū)樵~感到束手無策，因?yàn)橛⑽慕樵~種類繁多且詞意多變。不過，托福考試涉及的有關(guān)介詞的題目重復(fù)性很強(qiáng)，而且有規(guī)律可循。只要考生善于總結(jié)、記憶，還是可以保證得滿分的。
介詞的題目主要分布在Written Expression(16-40題)中，命題焦點(diǎn)：
(1)含有介詞的固定短語，(2)含有特定含義的介詞誤用
介詞常考題型及解題要點(diǎn)
1.含有介詞的固定短語：短語或詞組中的介詞不能隨意更換或省略
全真例題分析
(1)Most aquatic animals breathe by means external respiratory organs called gills.
答案：C 正確的短語為by means of，其中的介詞of不能省略
(2) Speed refers only toward the rate of mution without specifying any direction of motion.(94.8)
答案：A 正確短語形式為refer to
(3) Historical geology deals about data on the development of the Earth gathered from the study of rocks, which are analyzed to determine their age and composition. (93.8)
答案：A正確短語式式為deal with
(4)The diamond is the only gemstone composed with just one chemical element, carbon.
答案：A 正確短語形式為Be composed of
(5) Best known for his research in statistical mechanics and meson physics. Chen Ning Yang shared the Nobel Prize in 1957 to another physicist from the United States, Tsung-dao Lee.
答案：C 正確的短語搭配為share…with
(6)The doctrine of eminent domain is based the legal tradition that all real property is subject to the control of the state.
答案：A 正確的短語形式為be based on其中的介詞on不能省掉。
2. 介詞用錯
解題要點(diǎn)：介詞與后面的名詞通常有固定的搭配習(xí)慣，或有特定的語意功能，不能隨意更換。通常，介詞必有含義，不同的介詞會使整個句子表達(dá)不同的意思。當(dāng)A、B、C、D四個選擇答案中出現(xiàn)單獨(dú)劃線的介詞，應(yīng)首先考慮它是否使用正確。
全真例題分析
(1)Scientists claim that an individual can function from about three days when totally deprived of sleep.
答案：C from應(yīng)改用for，表示動作延續(xù)的時間應(yīng)用介詞for
(2) Canadian scarlet-clad guards and mounties with horseback are part of the summer scenery in Ottawa.
答案：B with改為on，“騎在馬背上”應(yīng)用介詞on表示位置
(3) During eclipses of the Sun, the Ojibwa Indians of North America shot flaming arrows inside the sky to rekindle the light.
答案：C inside改為into，介詞into表示的動作性；shot…into the sky，天空無邊無沿，不能用介詞inside來修飾
(4) Wild elephants are almost continuously waving their trunks. Both up in the air and down aside the ground.
答案：D aside改為on，on the ground 是固定介賓搭配。Ground 沒有邊沿，無法用aside來修飾
(5) Recent studies have shown that air into a house often has higher concentrations of contaminants than heavily polluted air outside.
答案：A into改為in，into強(qiáng)調(diào)動作，而in表示的是靜止的狀態(tài)。“房間里面的空氣”只能用in來表示
(6) The early use of a complete steel frame for towering buildings appeared in the first skyscraper, built on Chicago in 1883.
答案：D built on改為built in，城市名前面只能用介詞in來修飾
