Every possible means _______to prevent the air pollution, but the sky is still not clear.
| A．are being used | B．have been used | C．has been used | D．had been used |
The rescuers _______ to work as soon as they arrived at the spot of the accident.
| A．set out | B．set off | C．set up | D．set in |
I’ll never forget the good trick my classmates ________ on me when I was in the primary school.
| A．paid | B．acted | C．played | D．made |
Maybe Mr. Green is really in ______ debt, for he is losing ______ weight quickly.
| A．/ ; his | B．/ ; / | C．the; / | D．a; / |
________ many times, he still couldn’t understand it.
| A．Told | B．Being told | C．Having been told | D．Having told |
Always read the ______ on the bottle carefully and take the right amount of medicine.
| A．explanations | B．instructions | C．descriptions | D．introductions |