副词从句
从属连词（一般引起从句）:
after, when, before, as, while, since, until, till, although, though, if, even if, unless, lest, because, in that, than, that, whether, so that, as soon as, as long as, in order that, as if, as though, suppose (that), provided (that), in case (that), on condition (that), now that, so…that, such…that, as (so) …as, such…as
l 时间状语从句
1. They decided to chase the cow away_________ it did more damage.
a. unless b. until c. before d. although
2. I decided to go to the library as soon as I __________.
a. finish what I did b. finished what I did
c. would finish what I was doing d. finished what I was doing
3. A man escaped from the prison last night. It was a long time _____ the guards discovered what had happened.
a. before b. until c. since d. when
4. _____________ they reached the center of the city, they stopped the car at a bar.
a. Before a mile or so when b. For a mile or so after
c. Further than a mile or so d. A mile or so before
5. Scientists say it may be five or ten years ________ it is possible to test this medicine on human patients.
a. since b. when c. after d. before
6. I felt somewhat disappointed and was about to leave, ______ something occurred which attracted my attention.
a. unless b. until c. when d. while
7. You see the lightning ________ it happens, but you hear the thunder later.
a. the instant b. for an instant c. on the instant d. in an instant
8. I had just started back for the house to change my clothes ________ I heard voices.
a. as b. while c. after d. when
9. I was halfway back to the cottage where my mother lived _______ Susan caught up with me.
a. though b. until c. when d. while
