'用一般过去时代替完成时 1) 两个动作如按顺序发生，又不强调先后，或用then，and，but 等连词时，多用一般过去时。When she saw the mouse，she screamed.My aunt gave me a hat and I lost it. 2 ) 两个动作...'

'过去完成时典型例题 The students ___ busily when Miss Brown went to get a book she ___ in the office. A. had written, left B，were writing, has left C. had written, had left D. were writing, had ...'

'Mom, Sam and Kim are walking through a parking lotKim: I'm so excited to go to the store! I want lots and lots of candy! Mom: We'll see. Sam, Kim, stay right with me, OK?Kim: Don't worry, Mommy. ...'

'They enter Eagle grocery storeMom: OK, Sam. I want you on my right. Kim, you stay on my left. I'll push the cart.Sam: But I want to push the cart! Can I can I can I?Mom: OK, I guess you can do it...'

Sam and Kim rush off with the cart, leaving mom behind Sam: Get inside the cart, sis! I'll take you for a ride! Kim: Whee! Yeah! Faster! Faster! Sam: Daddy wanted beer, right? Let...

Sam and Kim get chocolate and beer and go to the toy aisle Sam: Look at this toy soldier! This gun is so cool. Kim: Hey! No fair. I don't have one yet! Sam: Bang, bang! Let's g...

'过去完成时 1） 概念：表示过去的过去其构成是had +过去分词构成。那时以前 那时 现在 2） 用法a. 在told, said, knew, heard, thought等动词后的宾语从句。She said (that) she had never been to Paris.b....'

'Twenty minutes later, Mom finds Sam and Kim shooting each otherMom: I'm going to take you back to the car right now! How dare you run off like that?Sam: But Mommy, we were just trying to help. Mo...'

'since的四种用法 1) since +过去一个时间点 (如具体的年、月、日期、钟点、1980, last month, half past six)。I have been here since 1989.2) since +一段时间+ agoI have been here since five months ago....'

'比较since和forSince 用来说明动作起始时间，for用来说明动作延续时间长度。I have lived here for more than twenty years.I have lived here since I was born..My aunt has worked in a clinic since 1949.S...'