Помогите расставить глаголы в правильной форме , и небольшое объяснение к каждому примеру. СРОЧНО

The tickets (to sell) _ two months ago. 2. Usually 3000 books (to buy) _ every week. 3. Recently the flight to China (delay) _because of the heavy rain. 4. As a result, at present hybrid cars and electric cars ( manufacture) _ as economical and Earth-friendly alternatives to conventional vehicles. 5. Much attention (pay) _____.

1.were sold2.are bought 3.delays4.are manufactured5.pays ,но я этого не поняла , будто незаконченнее предложение