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 |
Are you paying now, or shall I ＿＿＿＿＿＿ to you?
| A．book it down | B．book it in | C．book it up | D．book it out |
Please drop ＿＿＿＿＿＿＿ my home when you are free.
| A．in | B．on | C．in on | D．in at |
＿＿＿＿to my regret, I am unable to accept your warm invitation.
| A．Very | B．Much | C．Great | D．A lot |
We often say that something is “as light as air”, but air is＿＿＿light.
| A．hardly | B．rather | C．so | D．really |
The boy was＿＿＿＿＿＿eager to get a geography book.
| A．more | B．too | C．much | D．far |