一、用适当的介词＋关系代词完成句子。
1．I need to call my friend Mary, ________ ________ the book was left in my office.
答案 of whom
2．Eric received training in computer for one year, ________ ________ he found a job in a big company.
答案 after which
3．A lot of clubs have been organized in the school, ________ ________ students can get enriched and improve themselves.
答案 in which
4．The place ________ ________ the bridge is supposed to be built should be where the crossriver traffic is the heaviest.
答案 at which
5. Mark was a student at this university from 2002 to 2006, ________ ________ ________ he studied very hard and was made Chairman of the Students' Union.
答案 during which time
