You think Emma should book a seat on the train. Otherwise, she has to stand.
If Emma doesn't book a seat on the train, she'll have to stand.
Your room isn't clean, but you'd like to throw a party.
If my room was clean, I'd throw a party. / If I clean my room, I will throw a party.
Warn your friend not to put too many tins into the plastic bag or it'll break.
If you put too many tins into the plastic bag, it'll break.
You haven't got a pen, so you can't write down the address.
If I had a pen, I could write down the address.
You should start your project now. You don't want to work all night.
If start now, I won't have to work all night.
Your friend might need some help. If so, tell her to give you a ring.
If you need some/any help, give me a ring.
The automatic result of the door opening is the fan coming on.
If the door opens, the fan comes on.
I haven't got a key, so I can't get in.
If I had a key, I could get in.
You talk about football and I'm going to be very bored.
If you talk about football, I'm going to be very bored.
We want to have a good sleep. We hope the baby won't cry.
If the baby cries, we won't have a good sleep.
You may want a chat, so just give me a ring.
If you want a chat, just give me a ring.
Nigel hasn't got satellite TV, so he can't watch the game.
If Nigel had satellite TV, he could watch/would be able to watch the game.
You go away and I'll miss you.
If you go away, I'll miss you.
I'm not rich so I need to work.
If I was/were rich, I wouldn't need to work.
I'm afraid of spider or I'd have picked it up.
If I wasn't afraid of spiders, I would have picked it up.
You would like to buy that vase but you don't have enough money.
If I had enough money, I would buy that vase.
