john has worked as a sales manager since he (join)_joined____this company in 2002答案是joined 为什么呢

John　has　worked　as　a　sales　manager　since　he　（join）____this　company　in　2002. john has worked as a sales manager since he (join)_joined____this company in 2002答案是joined 为什么呢 ___ then,my mom has worked as a teacher. She _____ as a nurse ____ a year A.works;since B.has worked;for C.has worked ;since D.worked;for要原因,详细 he has worked as a teacher for only two weeks .he has little e ____ She has worked as a secretary for four years.句子中为什么要as? ( )Mr.John has worked in that small city __________ he left Canada in 1998.A.since B.for My aunt has worked as a secretary____2000.A.in B.since C.on D.for Mary has worked as a volunteer teacher for 10 years.翻译 he has worked as a report since 2000,根据since 2000提问? She has (work) as a nurse for three years.为什么填 worked 请说明原因, He works as a teacher now,but he ___ on a farm for 3 years.A.worked B.has worked C.had worked D.woHe works as a teacher now,but he ___ on a farm for 3 years.A.worked B.has worked C.had worked D.wokes答案给的是A,但是为什么不能选C过去完 he has worked as a teacher months ago改为he ( )to work as a teacher mongths ago Mr.white works as a journalist at present,but he ___in a high school for several yearsA.has worked B.worked C,had worked D.has been working 请详细说明为什么 She （ ）as an animal trainer since 2003 A.has worked B.works C.will work D.worked 并告诉我原因 Mike's father -- as an engineer for about ten years.A.worked B.works C.will work D.has worked为什么? ____ that time he has worked as a translator.A since B by C before D at选什么 为什么 He works as a teather now,but he__on a farm for three years .A.worked.B.has worked 请回答选A还是...He works as a teather now,but he__on a farm for three years .A.worked.B.has worked 请回答选A还是B并解释一下为什么