Ответ :

1. If the weather (is) nice, we will probably (go) to the beach. 2. If he still (has) a cold and (does not feel) better, he will not go to a disco. 3. If you (decide) to forget about your diet, you (will eat) a piece of wedding cake tomorrow. 4. If I (drink) too much champagne at my friend's wedding, I (will get) a bad headache. 5. If they (go) to California next year, they (will visit) his friend in San Francisco. 6. If she (does not  work) properly, her boss (will fire) her and (hire) my sister. 7. I (see) you before you (start)? 8. What (will he do) when he (comes) home? 9. Where will they (go) if the weathe ris  fine? 10. He (will ring) me up when he (returns) home. 11. If it (rains), we (will stay) at home. 12. She (will walk) home if it is not too cold. 13. I am sure he (will come) to say goodbye to us before he leaves  St Petersburg. 14. Please, turn off the light when you leave the room. 15. If we (get) tired, we (will stop) at a small village halfway to Moscow and (have) a short rest and a meal there. 16. If you (miss) the 10.30 train, there is another at 10.35. 17. She (will make) all the arrangements about it before she (flies) there. 18. Before he (starts) for London, he (will spend) a week or two at a holiday resort not far from here.