1. You made the same mistake for     third time, dropping_____ “u” in the word “unusual”.

A. a, the      B. a, a            C. the, an       D. a, an

2. —Which of the two pens are you going to buy?
—I’ll buy _____of them, so I can give one to my friend.
A. all           B. neither          C. every one       D. both

3. Oh, boy, why are you killing your time this way? Can’t you find something ________ doing?

A. useful          B. deserve           C. valuable        D. worth

4. He doesn't know_________ the work by himself.