Only in this way, _______succeed in solving the problem.
| A．you can | B．can you | C．you would | D．could you |
. He was told that it would be at least three more months __________ he could recover and return to work.
| A．when | B．before |
| C．since | D．that |
.Most birds find it safe to sleep in the trees, but __________ they have eggs or young chicks, they don’t use a nest.
| A．why | B．how |
| C．unless | D．where |
. Leave your key with a neighbor __________ you lock yourself out one day.
| A．ever since | B．even if |
| C．soon after | D．in case |
The news about the terrible flood there greatly discouraged __________ there for sightseeing.
| A．us from going | B．us to go | C．our going | D．our to go |
He's unlucky, and he's always suffering____________ luck one after another.
| A．a sick | B．an ill | C．sick | D．ill |