If we ... (can) come on Sunday, we ... (come). I'm really sorry we can't.
could / would come
If you ... (heat) water until it reaches 100 degrees, it ... (boil).
heat / boils
He ... (lose) weight if he ... (stop) eating so much. However, it's only an imagination!
would lose / stopped
Life ... (be) boring if we ... (have) nothing to do. It's great it isn't so!
would be / had
