1 who works at a plant? Where do his parents work?
2 What language does my sister study?
3 Who cleaned the blackboard after lesson? When did he clean the blackboard?
4 Where did he go to work? He went to work in the afternoon(не правильно, посмотрите) didn*t he?
5 When will she come back ? Will she come back at 3 or at 5 o*clock ?