____ has helped to protect the environment is worth praising.
| A．Who | B．The one |
| C．Anyone | D．Whoever |
We have produced 15% more cotton this year____ we did last year.
| A．as | B．than | C．like | D．white |
The teacher is busy ____ correcting papers.
| A．for | B．in | C．on | D．of |
____ the problem of method is solved, talking about the task is useless.
| A．Until | B．Since | C．After | D．Unless |
Where have you been ____ you left home?
| A．before | B．as | C．since | D．when |
____ you told me, I had heard nothing of what happened.
| A．Till | B．Until | C．After | D．Since |