if I do … 与 if I did的用法
比较这些例句:(1) LISA: Shall we take the bus or the train?
JESS: If we take the bus, it will be cheaper.
对杰西来说，他们可能会坐公交车，所以她说:
If we take the bus, it will be …
(2) Lisa and Jess decide to take the train.
Later, Jess talks to Joe.
JOE: How are you going to travel?
JESS: We’re going to take the train. If we took the bus,
it would be cheaper, but the train is quicker.
现在杰西知道他们不打算坐大巴了，所以她说：
If we took the bus, it would be …
当我们谈论不会发生的事情时，或者我们不希望发生， 我们用
If+过去((if we went / if there was 等等)。但它的意思并不是过去:
What would you do if you won a lot of money?
(I don’t really expect this to happen)
If there was an election tomorrow, who would
you vote for?
(there will not be an election tomorrow)
I’d be surprised if they didn’t come to the party.
(I expect them to come)
比较if I find 和 if I found:
I think I left my watch at your house. If you find it, can you call me?
但要说：If you found a wallet in the street, what would you do with it?
我们通常不会在句子的if部分使用would:
I’d be very scared if somebody pointed a gun at me. (not if somebody would point)
If we went by bus, it would be cheaper. (not If we would go)
在句子的另一部分(不是if部分)我们用would (' d) / wouldn’t:
I’d be (= I would be) scared if somebody pointed a gun at me.
I’m not going to bed yet. I’m not tired. If I went to bed now, I wouldn’t sleep.
What would you do if you were bitten by a snake?
Could 和 might 也是可能的表达方式:
If I won a lot of money, I might buy a house.
(= it is possible that I would buy a house)
If it stopped raining, we could go out.
(= we would be able to go out)
