Some students are net surfing．which does great harm to their physical and mental health
| A．addicted to | B．related to | C．addicting to | D．relating to |
China’s first compulsory safety regulation on primary buses, which requires every seat to have a seat belt, will ____ on July 1.
| A．have an effect | B．take effect | C．bring into effect | D．come to effect |
With smart phones taking the world by ____ storm, a phone that can only send and receive voice calls and text messages may seem like ____ relic.
| A．a; a | B．the; 不填 | C．the；a | D．不填; a |
We ______ last night, but we went to the concert instead.
| A．must have studied | B．might study |
| C．should have studied | D．would study |
— What does the sign over there read?
— No person ______ smoke or carry a lighted cigarette, or pipe in this area．
| A．will | B．must | C．may | D．shall |
．How long is it ______ we last spent the holiday in the country together?
| A．until | B．before | C．since | D．that |