If the weather is fine we'll have a picnic.
If she doesn't arrive soon we'll miss the train.
If it rains I'll take a taxi.
I''ll tell her if I see her.
If it rains I'll stay home.
If you don't know English you won't be able to get a decent job.
If you help me with all the housework I'll cook a delicious dinner for you.
If you see Mary, tell her the dress is ready.
If it gets too hot, open the window.
If you travel by train it takes much more time.