I.单句填空（每空1分，共10分）
1. The letter for the boss_______ (put) on his desk but he didn’t read them until three days later.
2. The earthquake was one of the worst natural _______ (disaster) the country has ever suffered.
3. They covered him with a blanket, only leaving his eyes______ (expose).
4. Don’t leave the water_______ (run) while you brush your teeth.
