The only season that makes one feel ________ is the spring．

A．lively

B．living

C．live

D．lovely

No one has ________ been able to trace the author of the poem．

A．still

B．yet

C．already

D．just

Our research has focused on a drug which is so ________ as to be able to change brain chemistry．

A．powerful

B．influential

C．monstrous

D．vigorous

Listen! His family must be quarrelling, ________?

A．mustn’t it

B．isn’t it

C．aren’t they

D．needn’t they

We hope to go to the beach tomorrow, but we won’t go ________ it’s raining．

A．if

B．when

C．though

D．because

In this factory, suggestions often have to wait for months before they are fully ________．

A．admitted

B．acknowledged

C．absorbed

D．considered

He must have passed this way, ________ here are his footprints．

A．since

B．because of

C．now that

D．for

－Why can’t you do it now?

－________ I’m too busy．

A．Since

B．As

C．Because

D．For

It was ________ he was ill that he was absent yesterday．

A．because

B．as

C．since

D．now that

I won’t tell you ________ something unexpected happens．

A．unless

B．whether

C．because

D．while