【正文】 It must be morning,for the birds are singing. 1) Parents should take seriously their children?s requests for sunglasses ____ eye protection is necessary in sunny weather.(?04上海） A. because B. though C. unless D. if 2) The changes in the city will cost quite a lot, ____ they will save us money in the long run.(?00全國春招） A. or B. since C. for D. but 目的狀語 從句： 通常由 that, so that, in order that, so…that, lest, in case（以防、免得）等引導： He got up early in order that he could catch the early bus. She married him so that she might tend and fort him. I explained again and again in case he should misunderstand me. 注意 : 目的狀語從句中謂語動詞常含有 may (might), can (could) should, will等情態(tài)動詞。如： When I was a boy, I used to go to the seashore on Sundays.（同時） When the lesson was over, we began our writing. （從句動作在前） 時間狀語從句： 引導時間狀語從句的從屬連詞有： when, while, as, whenever, before, after, since, till, until, as soon as, once,the moment, immediately, no sooner…than, hardly…when, by the time, every time, last time… 等引導。如： Don?t be afraid of asking for help_____ it is needed. (?03全國） A. Unless B. since C. although D. when *while可表示“雖然，盡管”。 （ 2） though與 although同義，用法基本一樣，前者通俗，口語化；后者較正式，多放于句首，不能與 but連用，但可以與 yet, still等連用，用來加強語氣。如： The struggle lasted four years before the North won in the end. He almost knocked me down before he saw me. 1) Someone called me up in the middle of the night, but they hung up ____ I could answer the phone.(?00全國） A. as B. since C. until D. before 2) He made a mistake, but then he corrected the situation ___ it got worse.(?03北京） A. until B. when C. before D. as (3)before “在 … 之前” Before I came downstairs I had prepared myself very carefully for what I must say. 3) Scientists say it may be five or six years____ it is possible to test this medicine on human patients.(?04福建） A. since B. after C. before D. when 4)It was evening _____ we reached the little town of Winchester.(?04天津 ） A. that B. until C. since D. before (4) by the time, each time, every time, immediately, the moment, the instant, the minute, soon after, shortly after都可以作為連詞，引導時間狀語。狀語從句 狀語從句在主從復合句中修飾主句中的動詞，形容詞或副詞，按意義可分為 時間、地點、原因、目的、結果、條件、方式、比較、讓步 等狀語從句。如： Until he returns, nothing can be done. 3) Was his father very strict with hi