--I thought I asked you to fix the radio.

--Oh, I'm sorry. I ________ it right now.

[　　]

A. am to do

B. will do

C. was about to do

D. am going to do

________ you should have no trouble with the difficult work.

[　　]

A. Knowing this

B. If you're knowing this

C. From knowing this

D. If you had known this

The number of people invited ________ fifty, but a number of them _________ absent for different reasons.

[　　]

The cakes are delicious. He'd like to have ________ third one because _________ second one is rather too small.

[　　]

Today is Sunday. There are _________ students playing football on the field.

[　　]

A. a good many of

B. much

C. a great deal of

D. a good many

Many people argue that ________ knowledge of computers is _________ must in modern times.

[　　]

The use of the word “except” is _________ from _________ of the word “besides”.

[　　]

A. different, one

B. difference, that

C. different, that

D. difference, one

Is there any new solution to _________ the kind of problem?

[　　]

You must do ________ you are told to.

[　　]

Little Sam said yesterday evening he would ________ me ________ a game of chess.

[　　]

A. challenge, of

B. challenge, to

C. challenge, by

D. challenge, at