________ the question of how global warming has _________, we are doing some projects at school.
| A．Exploring, come about | B．To explore, come out |
| C．Having explored, come to | D．Being explored, come over |
UN Secretary-General Ban Ki-moon left for Pakistan this morning， his assistant _________ him there this Friday.
| A．joins | B．joined | C．joining | D．to join |
The past two years _______ a sharp rise in oil price，which adds to the burden of auto transportation industry.
| A．witnessed | B．witnesses | C．is witnessing | D．has witnessed |
Mr. Duncan raised an unnecessary question __________ he then failed to find an answer.
| A．to which | B．for which | C．with which | D．by which |
Ｉdon’t think Linda could have done such a stupid thing last night，_________?
| A．do I | B．didn’t she | C． did she | D．don’t I |
My uncle hasn’t been able to quit smoking, but at least he has_________.
| A．cut out | B．cut down | C．cut up | D．cut off |