一、不定式和动名词作主语与表语的比较表示具体的、一次性的或将来的动作用不定式;表示一般的、泛指的或习惯性的行为用动名词。
如:◎ ________ is a good form of exercise for both young and old. (全国卷)
A. The walk                       
B. Walking
C. To walk                         
D. Walk
【分析】答案选B。a good form暗示泛指一般性行为,用动名词作主语。说明:①有时这种区别并不很严格。但要注意:主语和表语要用同一种形式;平行结构中要用同一种形式。

如:◎ —What do you think made Mary so upset? — ________ her new bike. (上海卷)
A. As she lost                     
B. Lost
C. Losing                           
D. Because of losing
【分析】答案选C。去掉问句中的插入语do you think,便知要回答的是主语what。选项中只有动名词Losing可作主语,全句应为:Losing her new bike made Mary so upset. 此处的动名词短语表示的是具体的一回事。

◎ The purpose of new technologies is to make life easier, ________ it more difficult. (全国卷)
A. not make                        
B. not to make
C. not making                     
D. do not make
【分析】答案选B。前面用的是不定式作表语,与之并列的也应用不定式。

◎ Fishing is his favorite hobby, and ________. (上海卷)
A. he’d like to collect coins as well          
B. he feels like collecting coins, too
C. to collect coins is also his hobby         
D. collecting coins also gives him great pleasure
【分析】答案选D。and连接两个并列句,前一分句用-ing形式作主语,与之并列的后一分句也应用-ing形式作主语。 ②通常只用动名词用主语的4种情况:在疑问句中;在It is no good / use…, It is useless…, There is no…等句型中;在某些动词的被动式前;在No smoking!之类的布告语中。如:1. Is doing morning exercises good for your health? 做早操对身体有益处吗?2. It’s useless arguing with them. 和他们讨论是没用的。3. Walking on the grass is forbidden. 禁止在这草地上行走。 ③通常只用不定式作主语的4种情况:在It is necessary / important / …(for sb. ) to do sth. 句型中;It is kind / foolish / …(of sb. ) to do sth. 句型中;在It takes sb. time to do sth. 型句中;主语被否定时。如:1. It is necessary for us to master a foreign language. 我们有必要掌握一门外语。2. It is very kind of you to help us. 你帮助我们真是太好了。3. It took me two hours to finish the work. 我完成那项工作用了两小时。4. Not to have hope is the poorest of all conditions. 绝望是最糟糕的事。
  
二、不定式、动名词、分词作表语的比较不定式和动名词作表语相当于名词作表语,表示主语的内容,主语和表语可以对调;分词作表语相当于形容词作表语,主语和表语不可对调;现在分词作表语表示主语所具有的性质特征,过去分词作表语表示主语所处的状态。如不定式和动名词作表语相当于名词作表语,表示主语的内容,主语和表语可以对调;分词1. My job is teaching / to teach English. (作表语的teaching / to teach English是my job的具体内容,可说成Teaching / To teach English is my job. )3. The movie is exciting. (exciting是主语the movie是性质特征。)4. They are excited at the news. (excited表示they现在所处的状态上海卷

【分析】答案选C。表示“就坐”的seat是及物动词,若后面没有sb. 或oneself作其宾语,就一定是seated,所以选C;此处的过去分词seated表示状态,remain=continue to be依然,保持。注:在seem, appear, prove(结果是、后来表明), remain(尚须)等连系动词后,可用不定式作表语,但不用-ing形式作表语。

如:Having a trip abroad is certainly good for the old couple, but it remains  ________ whether they will enjoy it. (全国卷)
A. to see                                    
B. to be seen
C. seeing                                    
D. seen
【分析】答案选B。remain作“尚须“解,后面通常接不定式;it(形式主语,指whether they will enjoy it)与see是被动关系,所以用不定式的被动式。