第1个回答 2010-06-20
从结构上说,英语连接词分两大类:并列连词(coordinating conjunctions)和从属连词(subordinating conjunctions)。 并列连词连接两个或两个以上地位平等的字、词组或分句。例如:(1) Air and water are indispensable to me. (2) She likes going out with friends or playing outdoor games. (3) Most workers have a good income, so they look very happy. 从属连词连接两个或两个以上的分句,形成复杂句中的从属分句。例如: (4) He said that he did not want to go . (5) Many things have happened since I last saw him. (6) You may come if you want to. 从属连词用来连接各种从句。until(till)直到,在用until表达时间状语的句子中,主句中的动词是要十分小心去选择的。如动词是持续行动词,它要用肯定句,如:I studied hard until 12 o'clock last night.如果动词是瞬间截止性动词,则要用否定句,如:He didn't go to bed until his mother came back.由since,for,by,before, 来引导的时间状语从句。since 引导的时间状语是动作的开始时间,如:I have studied English since 1990.而by引导的时间状语通常是动作的结束时间,如:I had learned 25 English songs by the end of last term.