第六单元第21课有下面两个句子：
1）It looks as if it isn't clean enough to bathe here．看来这海水不够干净，不能在这儿洗澡了。
2）It seems that there is a big waste pipe coming down from the town．看来有一根大废水管从城里一直接到这儿来了。
上述两句分别使用了look和seem常用的两个句型结构。除此之外，我们还学过appear一词，那么这三个表示“看来；似乎”的词常构成哪些句型结构呢？现将它们常用的几个句型结构归纳如下：
一、使用seem和appear的句型：
1．It seems ／appears（to sb．）＋ that-clause
It seems ／appears to me that they are right．我觉得他们似乎是正确的。
It seemed ／appeared that she enjoyed the food very much．看来她好像很喜欢吃这种食品。
2．Sb．／Sth．seems ／appears ＋to do
He seems ／appears to be a musician．他似乎是一个音乐家。
She seemed ／appeared to have caught a cold．她好像感冒了。
注：上述两种句型含义基本一样，都可作“看来／似乎是……”，且二者可相互转换。
He seems ／appears to have known about the secret．（＝It seems ／appears that he has known about the secret．）他似乎已知道这个秘密。
3There seems ／appears to be
There seems to be no difficulties to bediscussed．看来没有什么难题要讨论了。
There appears to have been a mistake．好像曾有错误。
二、使用look和seem的句型：
1．It looks ／seems as if．．．表示“看起来……；似乎……”。使用该句型应注意的是：若从句表示的是很可能实现的事情，从句谓语用陈述语气；若从句表示的是与事实相反的假设或实现的可能性很小的事情时，则从句谓语要用虚拟语气。
It seems as if he has been at the scene of the crime．看样子他好像曾在犯罪现场。
When a pencil is partly in a glass of water，it looks as if it were broken．如果把一枝铅笔的一部分放入水杯中，它看上去似乎是断了。
2．Sb．／Sth．looks ／seems like
The building looks like a school．这建筑物看起来像所学校。
It seems like years since I last saw you．自从我上次见到你以来，好像有几年了。
另注：seem，appear和look虽都有“看起来像”的意思，但三者仍有差别。 seem常含有基本接近事实的意义；appear多指从外表判断，一般与事实不符；look则着重指从外表而得到的印象，所得出的判断有可能与事实相符，也有可能与事实不符。
