是不是所有的英文句子都应有主谓宾?

是不是所有的英文句子都应有主谓宾?
什么时候没有主谓宾齐全?
举例子
并说明下句子各个成分

都是可以省略的.
为了避免重复,使语言简洁,英语中常常用多种方式省略句中某个成分；近凡年NMET单项选择题设计中,常有意省略试题中某些重要信息,增加试题难度.做这类题要注意语境分析,运用有关省略句知识,找出解题的关键.下面就中学英语课本中出现的省略现象加以归纳解析,供同学们复习时参考.
一、主语和谓语省略
1. --- Can I join your club, Dad?
--- You can when you____a bit older.
A. get B. will get C. are getting D. will have got
析:答案A.主句“you can”后承前省略了部分谓语“join our club”.
2. --- How long has this bookshop been in business.
--- ____1982.
A. After B.ln C.From D.Since
析:答案D.根据结构和句意,该题承前省略了整个主谓部分This bookshop has been in business, 只留下since 1982.
二、宾语省略
--- Do you think it's going to rain over the weekend?
--- ____.
A. I don't believe B. I don't believe it C. I believe not so D. I believe not
析:答案D.这是一个习惯表达法.很明显,该题省略了宾语从句,只留下了关键的否定副词not.完整句子为: 1 don't believe it's going to rain over the weekend. 这里也可以用I don’t believe so. So代替省略了的宾语从句.
三、比较级、最高级中的省略
The piano in the other shop will be____, but____.
A. cheaper; not as better B. more cheap: not as better
C. cheaper; not as good D. more cheap: not as good
析:答案C.从语境看,要表达的意思是“另一家商店的钢琴会便宜些,但不如（这家店的钢琴质量）好”,可见“not as good”是they are not as good as those in this shop的省略.
四、不定式的省略
1. --- Would you like to come to dinner tonight?
--- l’d like to, ____I’m too busy.
A. and B. so C. as D. but
析:答案D.根据语境,句意为“我今晚想去吃饭,但我太忙了不能去”.该题利用不定式的两次省略,为连词的选择设置障碍.把句子完整组织起来应该是:l’d like to (go to dinner tonight), but I’m too busy (to go).
2. The boy wanted to ride his bicycle in the street, but his mother told him____.
A. not to B. not to do C. not do it D. do not to
析:答案A.不定式符号to后原型动词省略,完整起来应是.“but his mother told him not to ride his bike in the street”.
另外,在中学英语课本中还常见其它一些结构性省略.如:
1. lt is said (that) he will leave for Shanghai on Sunday. (用it作形式主语时,主语从句中的that可省略.)
2. 1 was still so angry (that) I decided to tell him what I thought of him. （在so…that结构中,that可省略.）
3. lt is he (who/that) worked out the maths problem.（在强调句型“lt is... who/that”强调主语的结构中,who /that可省略.）
4. The books（that/which）you lent me were very useful. （关系代词在限制性定语从句中作宾语时可省略.)
5. He told me (that) you were a clever boy and that you were also honest. （宾语从句引导词that省略,但并列的宾语从句中,第一句的that 可略,其后的不可省略.）