7 Circle the correct answer. 1 We ...... stop polluting the environment. A don't have B have not C have to 2 They have been ...... up litter all morning. A pick B picking C picks 3 We ...... cook tonight. Cindy has invited us to dinner at her place. A must have B don't have to C have to 4 She doesn't work here anymore, ......? A is she B doesn't she C does she 5 You ...... to come with me. I can't go there on my own. A have B must C should 6 We've ...... a wonderful new car. A buy B bought C buying 7 You ...... study hard if you want to go to university. A have B must C need 8 You couldn't lend me £10 till the end of the week, ......? A did you B could you C will you 9 I've been ...... about you all day. A think B thought C thinking O Do I really ...... do my homework? A have to B must C should