He will come if you invite him
We'll go even if it rains.
I wonder if she is ill.
If I feel any doubt,I inquire.
If I were you,I would never do that
He will be home at six.
You will come,won't you
These things will happen
This auditorium will seat one thousand people
This will be the house you're looking for.
No one will leave the examination room before ten o'clock
If weather permits.
Ask if he is at home.
If I do not understand what he says,I always ask him.
If I haven't lost my watch!
If I only knew!
其实这些句子都是差不多的