seem,whether的用法和词性

seem,whether的用法和词性
seem,whether的用法和词性

seem,whether的用法和词性
seem可用作连系动词或不及物动词,意为“似乎；好像”,其常见用法现归纳如下：
一、“主语+ seem +（to be ）+表语”,表语多为名词或形容词,有时是其他的词或短语,以说明主语的特征或状态.例如：
Tom seems （to be ） a very clever boy.汤姆看上去是一个非常聪明的男孩.
The man over there seems to be a new teacher.那边的那个人看上去像一个新老师.
Mr Black seemed to be quite happy.布莱克先生好像十分快乐.
This small town seems changed a little.这个小城镇似乎有点儿变化.
二、“主语+ seem + 不定式”,此句型中的seem与不定式一起构成复合谓语.例如：
Mrs Green doesn’t seem （或seems not ） to like the idea.格林夫人似乎不太喜欢这个主意.
The children seemed to be eating something in the room.孩子们好像正在房间里吃东西呢.
The young man seemed to have changed much.这个年轻人看起来变化很大.
三、“It seems + that从句”,其中it 是形式主语,that引导主语从句.例如：
It seems that no one knows what has happened in the park.似乎没有人知道在公园里发生了什么事.
It seems to me that Mr Brown will not come again.在我看来布朗先生不会再来了.
四、“There + seem to be +名词”,其中to be 可省略.seem 的单复数形式要根据后面作主语的名词的单复数形式而定.例如：
There doesn’t seem to be much hope of our beating that team.看来我们战胜那个队没有多大希望.
There seems no need to wait longer.看来没有再等的必要了.
whether和if的用法区别
whether与if作“是否”讲,在用法上有相同之处,也有不同之处.
一、相同之处.
1.whether和if都能引导宾语从句,常置于see,ask,learn,tell,wonder,doubt,find out等动词之后.
如：He asked me whether/is I could help him.I want to know whether/if he lives there.
2.whether和if都可用it作形式主语从句中.如：it's uncertain whether/if he'll come this evening.
3.在be uncertain/doubtful之后,常用whether引导宾语从句,有时也可以用if,如：We are uncertain whether/if Mary will come.
二、不同之处.
1.whether可置于句首引导主语从句,而if不能.如：___the 2000 Olympic Games will be in Beijing is not known yet.A.whether B.If C.Whether D.That 答案是C.
2.whether可用在介词之后,引导宾语从句,而If则不能.如：Success depends on whether we make evough effort.
3.whether可引导表语从句,if则不能.如：The puestion is whether it is not worthdoing.
4.在名词之后引导同位语从句时,用whether而不用if.如：The puestion whether the students answered correctly should be decided by the teacher.
5.whether后可接不定式,而if不能.如：Please tell us whether to go or stay here.
6.在有些动词（如discuss）之后,只能用whether,而不用if引导宾语从句.如：We discussed whether we should close the shop.
7.在引导否定概念in宾语从句时,只能用if,而不用whether.如：he asked me if I hadn't finished my work.
I don`t know whether he will go.可以