25 翻译：你长大了想当什么？（when or if?）

A: What time will you phone me tomorrow?
B: I will phone you when I get home from work.
第2句话I'll phone you when I get home from work可以分成两个部分，主体部分是 I'll phone you,再加一个引导的从句： when I get home from work.
主句的时态是将来时，但是在When引导的从句里我们用了一个现在时态（get）

when引导的表示将来的从句我们不能用will来表达。
-We will go out when it stops raining.
-When you are in London again, you must come and see us.
-What do you want to be when you grow up?

类似的词语还有 while/ before/ after /as soon as/ until/ till/ hope

-I'm going to read a lot of books while I'm on holiday.
-I'm going back home on Sunday.
Before I go, I'd like to visit the museum, -Wait here until I come back.

另外，在 when /after /until /as soon as后面我们也可以用现在完成时：
-Can I borrow that book when you've finished it?
-Don't say anything while Ian is here. Wait until he has gone.

通常情况下用现在完成时和一般现在时都可以。
-I'll come as soon as I finish.
-I'll come as soon as I've finished it.
——
-You'll feel better after you have something to eat.
-You'll feel better after you've had something to eat.

但是咱两件事情一起发生的时候不可以用现在完成时。 因为现在完成时已经表达了一件事情比另一件事情结束的早。所以两件事情不可能同时发生。
The present perfect shows that one thing will be completed before the other. So the two things do not happen together:
-When I've phoned Kate, we can have dinner.（ =First I'll phone kate and after that we can have dinner.）
But
-When I phone Kate this evening, I'll invite her to the party.（Not when I've phoned. In this example, the two things happen together.）
——
在if 后我们通常用一般现在时（if I do/ if I see etc.）表示将来：
It's raining hard. Waiter, get wet! If we go out, hurry up. If we don't hurry, we will be late.

比较when 和 if：
We use 'when' for things which are sure to happen.我们用when来表达确定要发生的事情：
-I'm going shopping this afternoon.（for sure） When I go shopping, I'll buy some food.
We use if（ not when） for things that will possibly happen:
-I might go shopping this afternoon.（ It's possible. )If I go shopping, I'll buy some food.
-If it is raining this evening, I won't go out. （Not 'when it is raining'.）
-Don't worry if I'm late tonight.（ Not 'when I'm late'.）
-If they don't come soon, I'm not going to wait. （Not 'when they don't come'.）