OKRES I – If + Present Simple + Future Simple. If I meet Paul, I’ll give it to him. If don’t study hard, you will fail your examination. John will not be happy if he sees it. OKRES II - If + Past simple + Future in the past. If I met Paul, I would give it to him. If I had more time, I would travel more often. If I earned more, my wife could stay home and look after the children. OKRES III – If + Past Prefect + Future in the Past. If I had met Paul, I would have given it to him. If I had known your telephone number, I would have phoned you. We would have won easily if Tom had played in our team. We might have met him if we had left earlier. PAST PERFECT – I had gone / seen / finished. I had never seen her before. He had never played tennis before.