帮忙分析两个句子的语法,Welcome to Beijing!I's the most amazing iPhone yet.第一个句子什么时态?第二个为什么有yet?第二个错了：It's the most amazing iPhone yet.

帮忙分析两个句子的语法,Welcome to Beijing!I's the most amazing iPhone yet.第一个句子什么时态?第二个为什么有yet?第二个错了：It's the most amazing iPhone yet.
帮忙分析两个句子的语法,
Welcome to Beijing!
I's the most amazing iPhone yet.
第一个句子什么时态?第二个为什么有yet?
第二个错了：
It's the most amazing iPhone yet.

帮忙分析两个句子的语法,Welcome to Beijing!I's the most amazing iPhone yet.第一个句子什么时态?第二个为什么有yet?第二个错了：It's the most amazing iPhone yet.
Welcome to Beijing!
I's the most amazing iPhone yet.
第一个句子什么时态?第二个为什么有yet?
答：第一句是一个省略句,完整的句子是：You are welcome to Beijing.其中的welcome是形容词.
与Happy new year!中的happy一样,并不是动词.
知道了完整的句子后就知道它的时态了：一般现在时.
但说它是祈使句是误会.这个welcome不是动词原形.这句话既不是请求（祈）也不是命令（使）.
It's the most amazing iPhone yet.一句中的yet的用法与我们平时所见到的yet的用法不一样：
朗文当代英语词典
yet 1
yet1 W1S1 /jet/ adv
[Language:Old English; Origin:giet]
a) used in negative statements and questions to talk about whether something that was expected has happened
　I haven't asked him yet (=but I will) .
　Has Edmund arrived yet?
　'Have you finished your homework?' ' Not yet .'
b) used in negative statements and questions to talk about whether a situation has started to exist
　'How are you going to get there?' 'I don't know yet.'
　Women didn't yet have the vote (=at that time) .
　'Is supper ready?' 'No,not yet .'
used in negative sentences to say that someone should not or need not do something now,although they may have to do it later
　You can't give up yet!
　Don't go yet.I like talking to you.
used to emphasize that something is even more than it was before or is in addition to what existed before
= still
yet more/bigger/higher etc
　He got a call from the factory,telling of yet more problems.
　Inflation had risen to a yet higher level.
yet another reason to be cautious
　The meeting has been cancelled yet again (=one more time after many others) .
the biggest/worst etc (sth) yet
used to say that something is the biggest,worst etc of its kind that has existed up to now
　This could turn out to be our biggest mistake yet.
　Nordstrom's latest novel looks like his best yet.
属于最后这一种.

第一个句子是祈使句，祈使句一般都用一般现在时态

第一个是一般现在时；第二个应该是强调作用吧？！

第一个是祈使句，祈使句都是一般现在时，第二个你打错了吧，I's那是什么啊，在我的记忆当中yet似乎用在否定句中。

第一个句子是祈使句，祈使句一般都用一般现在时态

第一个句子是祈使句，祈使句一般都用一般现在时态 Open the window. Close the door.
第二个是最高级 The question is the most difficult of all.