1. We cook tonight. Cindy has invited us to dinner at her place 1) must have 2) don't have to 3) have to 2. You to come with me. I can't go there on my own 1) have 2) must 3) should 3. We've a wonderful new car 1) buy 2) bought 3) buying 4. I've been do my homework? 1) think 2) thought 3) thinking 5. We stop polluting the environment 1) don't have 2) have not 3) have to 6. They have been up litter all morning 1) pick 2) picking 3) picks