语法专项练习---------现在完成时41. 现在完成时通常可与表示过去不确定时间的时间状语连用，如already, yet, just, before等副词时间状语。
例子见上述“主要用法”中。
例如：1）I have already returned the pen to him.2）Have you washed my clothes yet? ----Yes, I have just washed them.3）I have seen the man before.说明：before有时也可用于一般过去时（这与用现在完成时意思差不多），如I told you before.我早就告诉过你。
2. 现在完成时通常可以与包括“现在”在内的表示一段时间的时间状语连用，如since..., for...；ever, never,recently（最近），today, this week (year), these days (weeks, years), in/during the last/past two years, so far等。
例如：1）We have known each other since we came to the school.2）I have collected ten stamps this week[these weeks].3）Have you seen him these days?说明：ever, never有时也可用于一般过去时（这与用现在完成时意思差不多），如I never saw the man.※区别用法1. already与yet一般情况下，already表示“已经”，主要用于肯定陈述句，一般在句中；yet表示“已经”或“仍然，还”是用于疑问句或否定句，一般在句末。
比较：1）He has already come.2）Has he come yet?3）He hasn’t come yet.2. ever与yetever与yet均可用于疑问句、否定句，但yet表示“已经”或“仍然，还”，一般“时间上距离现在不是很远”；ever表示“曾经，以往任何时候”，“时间上距离现在可近可远”，反义词never。
体会：1）Have you ever milked a cow? 你曾经挤过牛奶吗？----No, I never have.或No, never. 没有，从来没有过。
（问可以是有生以来的经历）2）Have you milked the cow yet? 你已经给那头牛挤过奶了吗？----No, I haven’t yet.或No, not yet.（问现在说话说时的情况）3. for与sincefor和since均可引导一个时间状语，与现在完成时连用，区别如下：“for + 一段时间”，意思为“共计……（时间）”；for是prep.，后面只能跟一个短语，即只能引导一个时间短语。
“since + 某一时间”，意思为“自从……（以来）”；since是prep.&conj.，后面可以跟一个短语，也可以跟一个句子，即既可以引导一个时间短语，也可以引导一个时间从句。
例如：1）He has sat here since two o’clock.He has sat here since he came here.2）He has sat here for two hours.4. two years ago与for two years, since two years ago 三者的意思和连用的时态不一样：例如：1）He lived here two years ago. 他两年前住在这儿。
（已有两年不住在这儿了）2）He has lived here for two years. 他在这儿住两年了。
（两年前开始住的，一直住到现在，还可能继续住下去）比较：He lived here for two years. 他过去（曾经）在这儿住两年了。
（是哪两年不清楚）He has lived here since two years ago. 两年来，他一直住在这儿。
练习用since和for填空______two years ____two years ago ___last month ______ 1999 _______yesterday _______ 4 o’clock _______ 4 hours _____an hour ago___we were children _____ lunch time ____ she left here1. He has lived in Nanjing _______ the year before last.2. I’ve known him ______ we were children.3. Our teacher has studied Japanese ______ three years.4. She has been away from the city ______ about ten years.5. It’s about ten years __________ she left the city.6. Jim has been in Ireland ______ Monday.7. Jill has been in Ireland ______ three days.8. His aunt has lived in Australia ______15 days.9. Mary is in her office. She has been there ______ 7 o'clock.10. India has been an independent country ______1974.11. The bus is late. They've been waiting ______ 20 minutes.12. Nobody lives in those houses. They have been empty ______ many years.13. Mike has been ill ______a long time. He has been in hospital ______ October.用never, ever, already, just, yet, for, since 填空.1. I have ___________ seen him before, so I have no idea about him.2. Jack has _____________ finished his homework.3. Mr. Wang has taught in this school ____________ ten years.4. “Have you ____________ seen the film?” “No, I have ____________ seen it.”5. “Has the bus left ___________?” “Yes, it has _____________ left.”用动词的适当形式填空1.She‟s _____________ (live) here ever since she was ten.2.Both of them ________________ (be) in Hong Kong for ten days.3.Both of them ____________ (come) to Hong Kong ten days ago.4. Half an hour __________ (pass) since the train __________ (leave).5. Mary________(lose) her pen. ________ you _______(see) it here and there?6. _________ you _____ (find) your watch yet?7. ---Are you thirsty? ---No, I _________just _________ (have) some orange.8. We _________ already _________ (return) the book.9. ________ they _______ (build) a new school in the village?10. I _____________ (not finish) my homework. Can you help me?11. My father _____ (read) the novel twice.12. I _________ (buy) a book just now.13.-Mum,may I go out and play basketball?-______you______（finish）your homework yet?14. My father ___________ (read) this book since yesterday.15. I____ already ____ (see) the film. I ________ (see) it last week.16. My mother __________ (come) to see me next Sunday.17. My father ____ just ____ (come) back from work. He is tired now.18. Where’s Li Ming? He __________ (go) to the teacher’s office.19. I __________ (work) here since I ______ (move) here in 1999.20. So far, I _______________(make) quite a few friends here.21. How long ________ the Wangs ______________(stay) here? For two weeks.22. I ________ just ___________ (finish) my homework.23. He ________ (go) to school on foot every day.24.____ you ______ (find) your science book yet?25. Look! The monkey __________ (climb) the tree.。