——How do you like the set of popular science books?
——Wonderful! It _____ many problems we are interested in exploring.
| A．refers | B．consults | C．covers | D．writes |
We have realised that ____ is much that can be done to help improve our environment.
| A．what | B．it | C．there | D．one |
.I doubt very much _____ the tickets for tomorrow have _____.
A that ; been sold away B that ; been sold out
C if ; sold out D whether ; been sold out.
It is playing computer games _______ he spends so much time that he fails all the exams
| A．which | B．what | C．in which | D．that |
The train he was looking forward to ______ only a few minutes ago.
A arrives B arrived
C arriving D had arrived
Persons under 16 ______ not be employed in our country．
| A．shall | B．can | C．may | D．will |