1.last night when we [visit].....visited.....him,he [learn]......was learning.....his lessons for the test upstairs.
2.the ewing machine which you [use].....are using.....at present [invent].......was invented......in 1830 by a frenchman
3.do you know what is this pudding [made].........made........from
4.I [watch]......was watching......TV while my mother [read] ......was reading.....last night
5.Nam [go]........went..........out with his friends two hours ago