| In the past twenty years, many tall buildings have been built in our city. Look! This is a . |
A. 70-floor building B. 70-floors building C. 70-floor buildings D. 70 floors building |
| — has Bob been collecting stamps? — Since he was 8 years old. |
A. How often B. How long C. When D. How much |
| — How long has the nationwide ban (禁止) on plastic bags been put into practice? — the beginning of June. |
A. Behind B. Since C. For D. At |
| — Will you come to the net bars (网吧) with me? — Sorry. My mother always tells me ____ there. |
A. not go B. go C. not to go D. to go |