在高三課本第十五單元出現(xiàn)了下面幾個(gè)句子：
1 As Kofi Anna，Secretary General of the United States said，“each contribution -- how small -- can help make a difference.”
2 Now she is spending a year in remote part of southwest China working as a volunteer teacher in a village school.
這幾個(gè)句子都涉及到了as的用法。作介詞用，第一句話中as用作關(guān)系代詞，引導(dǎo)定語(yǔ)從句，含義為“正如”，第二句話中as的含義為“作為，當(dāng)作”，做介詞。
下面讓我們結(jié)合歷年高考試題對(duì)其用法進(jìn)行分析。
一.用作連詞引導(dǎo)讓步狀語(yǔ)從句
從句必須用倒裝語(yǔ)序，把作表語(yǔ)用的名詞(不加冠詞)或作表語(yǔ)的形容詞，或動(dòng)詞(原形)，或副詞提到as前面。如：
1.Child as he is，he knows a lot.
2.Tired as they were，they stayed up late preparing for the coming exams.
3.Try as he would，he failed again this time.
考例：1.(2005重慶)___，he talks a lot about his favorite singers after class.
A.A quiet student as he may be
B.Quiet student as he may be
C.Be a quiet student as he may be
D.Quiet as he may be a student
【解析】答案是B。作表語(yǔ)的是名詞student，名詞前不加冠詞。
2.(2005.廣東)____，Carolina，couldn’t get the door open.
A.Try as she might B.As she might be C.She might as try D.Might she as try
【解析】答案是A。as引導(dǎo)讓步狀語(yǔ)，將動(dòng)詞原形try提到as前面。
二.用作關(guān)系代詞，引導(dǎo)定語(yǔ)從句
as用作關(guān)系代詞，引導(dǎo)定語(yǔ)從句，含義為“正如”。如：
1.He is very careful，as his work shows.
2.As is known is reported in the newspaper，talks between the two countries are making progress.
考例：(2005浙江)___I explained on the phone，your re quest will be considered at the next morning.
A.When B.After C.As D.Since
【解析】答案是C。意思是“正如我在電話里解釋的那樣……”。
2.(2006)The Beatles，____many of you are old enough to remember，came from Liverpool.
A.what B.that C.how D.as
【解析】答案是D。引導(dǎo)非限制性定語(yǔ)從句。
三.作為副詞
用于表示“和……一樣，”的意思，as…as中間要用形容詞/副詞的原級(jí)，如as long as：長(zhǎng)達(dá);as far as遠(yuǎn)達(dá);as much as：多達(dá);as tall as含義為“高達(dá)…”。如：
That day they walked as far as ten kilometers in two hours.
考例：(2005安徽)John is the tallest boy in the class，_______according to himself.
A.five foot eight as tall as B.as tall as five foot eight C.as five foot eight tall as D.as tall five foot eight as
【解析】選B.as…as中間要用形容詞/副詞的原級(jí)。
四.引導(dǎo)時(shí)間狀語(yǔ)從句
含義為“當(dāng)…的時(shí)候”，如：
1.I watched her as she combed her hair.
2.As he grew older ，he lost interest in everything except gardening.
考例：1.(NMET1994)Mother was worried because little Alice was ill，especially____Father was away in France.
A.as B.that C.during D.if
【解析】答案是A.“在……時(shí)候”，相當(dāng)于when.而C選項(xiàng)是介詞，不接句子。
2.(MET90)_____the day went on，the weather got worse.
A.With B.Since C.While D.As
【解析】答案是D.“隨著”的意思，as the day went on可以作為固定結(jié)構(gòu)記住。
五.作介詞用
有“作為，當(dāng)作”的意思。如：
1.They were all dressed as clowns.他們都打扮得如小丑。
考例：(2005廣東)I feel that one of my main duties_____a teacher is to help the students to become better learners.
A.for B.by C.as D.with
【解析】選C。“作為教師”的意思。
