Correct the errors in the following sentences. 1. He was not due at the office for another three-quarter of an hour. 2. This is the worst disaster I can remember in my plus 25 years as a police officer. 3. It took him one and a half hour to finish the task. 4. Five hundred yuan a month are enough to live on. 5. Three fourth of the buildings was ruined. 6. He is a student of the Class Two.