关于it is的用法
以下这些例子有助于防止把这两种形式混淆：
A it is+形容词;there is+名词：
It is foggy./There is a fog.
有雾。
It was very wet./There was a lot of rain.
很湿。/下了不少雨。
It wont be very sunny./There wont be much sun.
天气不会很晴朗。
B it is与there is都可以表示时间和距离：
It is a long way to York.
到约克路很远。
There is a long way still to go.
还有很长的路要走。(我们还有好多英里的路程。)It is time to go home.
该回家了。(我们一般是6点回家而现在6点了。)
There is time for us to go home and come back here again before the filmstarts.
在电影开演之前我们有时间先回家一趟再回到这里。(还有足够的时间)
C there is+名词/代词和用于识别人或物的 it is+名词/代词的比较：
There is someone at the door.I think its the man to read the meters.
门口有个人。我想他是来抄(水、电等)表的。
There is a key here.Is it the key of the safe?
这里有一把钥匙。是开保险箱的吗?
D 用于分裂句的it is()以及there is的比较：
It is the grandmother who makes the decisions.
做出决定的是老奶奶。(是老奶奶而不是家里的其他成员)
and theres the grandmother，who lives in the granny-flat.
还有老奶奶，住在专用套房里的那位。(有老奶奶其人)