Period Three Grammar基础落实Ⅰ.用所给词的适当形式填空1.By the end of yesterday,we had ________(receive) over 1,000 letters from all over the world.2.He didn’t go to bed until he ________________(finish) his work.【来源:21·世纪·教育·网】3.She ________________(study) English for several years before she went there.4.I ________________(be) at the bus stop for 20 minutes when a bus