動(dòng)詞及其非謂語動(dòng)詞形式一直是各類考試中的熱點(diǎn),更是我們?cè)谌粘＝虒W(xué)中的難點(diǎn), 尤其是置于句首時(shí)該用何種形式更讓學(xué)生頭疼.其實(shí)只要我們掌握了它們的使用規(guī)律,要想做好這類題也不是難事.本文要討論一下動(dòng)詞及其非謂語動(dòng)詞置于句首時(shí)該如何判別其正確形式.
一．動(dòng)詞原形
動(dòng)詞原形置于句首,毫無疑問應(yīng)該是祈使句.祈使句的考查形式多是“句子+連詞+句子”, 最常見的連詞有and, or, otherwise, even though 等.所以判別的時(shí)候先看一下后邊是否有一個(gè)“連詞+句子”的形式；如果有,則句首的空格一定要填動(dòng)詞原形.連詞前可以有逗號(hào),也可以沒有.
例1．
--English has a large vocabulary, hasn’t it?
--Yes. __ more words and expressions and you’ll find it easier to read and communicate.(04上海高考-44)
A. KnowB. Knowing C. To knowD. Known
答案選A. 因?yàn)楹筮呌幸粋€(gè)連詞and, 其后是一個(gè)完整的句子,前半部分中沒有主語,則一定是祈使句.
一．動(dòng)詞不定式
動(dòng)詞不定式置于句首,有兩種功能,一種是做主語,另一種是做目的狀語.
(一) 動(dòng)詞不定式做主語, 通常有兩種情形: 一種是不定式直接放在句首(這種形式較少),另一種是用it做形式主語,把不定式置于句末,達(dá)到平衡句子的目的.
eg. To see is to believe.
It’s nice of you to help me with my English.
(二) 不定式置于句首做目的狀語是考查的重點(diǎn), 其后通常有逗號(hào)與主句隔開,相當(dāng)于in order to.
例2 ____ this cake, you’ll need 2 eggs, 175g sugar and 175g flour.
A. Having made B. Make C. To make D. Making(06 廣東高考-30)
答案選C. To make 表目的,相當(dāng)于In order to make.
例3 –Can the project be finished as planned?
--Sure, __ it completed in time, we’ll work two more hours a day.(05 福建高考-29)
A. having got B. to getC. getting D. get
答案選B. to get表目的, 相當(dāng)于In order to get.
三. V-ing 形式置于句首
V-ing 既可以是動(dòng)名詞,也可以是現(xiàn)在分詞.
(一) 動(dòng)名詞置于句首,做主語,常表示概括性的或一般性的行為.
例4 ___ to sunlight for too much time will do harm to one’s skin.(02 上海高考-38)
A. Exposed B. Having exposed C. Being exposed D. After being exposed
答案選C. Being exposed to sunlight for too much time 在句中做主語.
需要注意的是, 動(dòng)名詞做主語和表語應(yīng)遵循對(duì)稱原則,即: 主語用動(dòng)名詞時(shí), 表語也用動(dòng)名詞. 例如, Seeing is believing.
(二) 現(xiàn)在分詞置于句首,做狀語,表明分詞的邏輯主語與主句的邏輯主語一致,其否定形式是not doing. 如果分詞所表達(dá)的動(dòng)作明顯先于主句謂語動(dòng)詞的動(dòng)作,則用其完成形式having done, 否定形式是not having done.
例5, My cousin came to see me from the country, ___ me a full basket of fresh fruits.(06安徽高考-21)
A. broughtB. bringing C. to bringD. had brought
答案選B. bringing在句中作伴隨情況狀語,其邏輯主語就是句子的主語my cousin.
現(xiàn)在分詞視情況,有時(shí)其前面可以加上when, while, after, before, if, though, whether, unless 等連詞, 這時(shí)相當(dāng)于 “連詞+主語(主句主語或it)+ be +v-ing” 形式分句作狀語時(shí)的省略.
例6
When __ different cultures, we often pay attention only to the differences without noticing the many similarities.(o6浙江高考-5)
A. comparedB. being comparedC. comparingD. having compared
答案選C. 分詞短語相當(dāng)于狀語從句 when we are comparing different cultures.
有些經(jīng)常用于句首的-ing 形式短語已經(jīng)轉(zhuǎn)換成介詞, 主要有 according to 根據(jù), judging from 從……判斷, talking of 談到, taking all things into consideration 全盤考慮, setting aside 除開等. 另外還有一種常見的 “ 副詞+speaking”結(jié)構(gòu)置于句首做整個(gè)句子的狀語.
Judging from her accent, she must be an American.
Taking all things into consideration, I think he is a very honest man.
Frankly speaking, his article still needs more revising.
四. 過去分詞置于句首
過去分詞置于句首做狀語, 通常表示被動(dòng)或完成, 說明謂語發(fā)生的背景或情況.
例7. ___ automatically, the e-mail will be received by all the club members.(06 上海高考-40)
A. Mailed outB. Mailing out C. To be mailed outD. Having mailed out
答案選A. 分詞短語作狀語, 相當(dāng)于一個(gè)假設(shè)條件狀語從句If it is mailed automatically, e-mail 與mail out 是被動(dòng)關(guān)系.
例8. __ for the breakdown of the school computer network, Alice was in low spirits.(06 福建高考-33)
A. Blaming B. BlamedC. To blameD. To be blamed
答案選B. 非謂語動(dòng)詞形式作原因狀語,主語是blame所表達(dá)動(dòng)作的承受者, 因而用過去分詞blamed.
過去分詞置于句首還有一種比較特殊的結(jié)構(gòu), 即 “be+ 過去分詞+ 介詞” 結(jié)構(gòu)表示狀態(tài)的短語變化而來, 也就是 “be+ 過去分詞+ 介詞” 短語置于句首表示狀態(tài)時(shí), 可以直接省略掉be動(dòng)詞.
例9. __ with so much trouble, we failed to complete the task on time. (06 四川高考-33)
A. FacedB. FaceC. FacingD. To face
答案選A. 可以將該分詞結(jié)構(gòu)看作是be faced with 短語置于句首作原因狀語的省略.
同現(xiàn)在分詞作狀語時(shí)前面可以加when, while, though, if 等連詞的情況一樣,過去分詞前也常加一些連詞.
例10. When first __ to the market, these products enjoyed great success. (04 四川高考-22)
A. introducing B. introduced C. introduce D. being introduced
答案選B.非謂語動(dòng)詞短語相當(dāng)于when these products were first introduced to the market作狀語的省略.
五. 獨(dú)立主格結(jié)構(gòu)
英語中最常見的獨(dú)立主格結(jié)構(gòu)就是 “名詞(代詞) + 現(xiàn)在（或過去）分詞,位于句首做狀語．在這種結(jié)構(gòu)中,名詞或代詞是分詞形式的邏輯主語,在意義上可以表示時(shí)間,條件,原因,伴隨狀況等,現(xiàn)在分詞表主動(dòng),過去分詞表被動(dòng)．
Weather permitting, we will go picnic tomorrow.
The question settled, the meeting was over.
動(dòng)詞及其非謂語動(dòng)詞形式的用法看似復(fù)雜,實(shí)際上我們只要分析好句子成分及該動(dòng)詞在句中的角色,就比較容易把握好適當(dāng)?shù)男问搅耍?div style="margin-top:20px">