分类：教育/科学-外语学习
问题：什么是时间状语 
回答：A 时间状语从句:连接时间状语从句的连接词有: (1) 连词：when, while, as. 它们都表示当…时候的意思。如果主句和从句的动作同时发生且都是进行时　　　 　态，只用while, as. 其他情况下when, while, as。１　When he came in, I was listening to the radio．２　As I was wandering in the street, I met her.３　While (as) I was watching TV, my mum was cooking in the kitchen.(2) 连词before, after, since, until(till). 当他们表示时间时，他们既是介词又是连词。{ He usually drinks a cup of tea before he goes to school.　　　　　　　　　　　　　　　　　 连词 He usually drinks a cup of tea before going to school. 　　　　　　　　　　　　　　　　　介词  { He usually drinks a cup of coffee after he comes back from school.　　　　　　　　　　　　　　　　　 　连词 He usually drinks a cup of coffee after coming back from school. 　　　　　　　　　　　　　　　　　　　介词  { I have lived in Dalian since my son was born in 1999.　　　　　　　　　　　　 连词通常情况下，主句用现在完成时，从句用一般过去时。I have lived in Dalian since 1999.　　　　　　　　　　　　　介词  { I will wait here until(till) you finish your job.　　　　　　　　　　　 连词I will wait here until(till) 8pm.　　　　　　　　　　　介词  (3) 词组：as soon as{ I will tell him as soon as he comes back.As soon as she finishes her homework, she will play tennis.通常情况下，主句用一般将来时，as soon as 引导的从句用一般现在时。