Police in America have stepped up their search for a fifteen-year-old boy who went _____ three days ago.
A. going B. losing
C. missing D. disappearing
There are _____ flights between the two cities, _____ it convenient for people in one city to travel to work in the other.
A. regular; to make B. usual; making
C. usual; having made D. regular, making
Though faced with so many difficulties, they are _____ about their future.
A. curious B. enthusiastic
C. optimistic D. concerned
The Sahara Desert is almost _____ of the US.
A. as big B. the size
C. the area D. the same
We shall never forget the days ________ we spent playing happily together.
A. in which B. which C. when D. on which
______ is said, the Yeti is a large, hairy animal that walks on two feet like a human being.
A. It B. That C. As D. What
