We should be aware _______the problem facing the world.
A. of
B. to
C. with
D. about
4. Last year, my class _______ to teach the children in a remote area.
A. volunteer
B. voluntary
C. volunteered
D. volunteers
5. Thomas Edison, Benjamin Franklin, James Watt are among of the greatest ____ of all time.
A. inventions
B. inventiveness
C. inventors
D. invents
6. Many young people carry a pair of earbuds as they are small, light, and ____.
A. chargeable
B. economical
C. portable
D. transferable
7. We can surf the ____ to search for news, watch films, or download music.
A. e-book
B. internet
C. laptop
D. smartphone