Combine each pair of sentences using relative pronouns

Combine each pair of sentences using relative pronouns. 

1. We've just seen a professor. He is going to give a lecture at our school tomorrow. 

2. The man was painting the ceiling. He fell off the ladder.

3. The girl is very good at mathematics. She sits next to me. 

4. I'm looking forward to meeting an old friend. I haven't seem him for two years.

5. We invited an actor to our school last Sunday. He gave a wonderful performance.

6. The police have caught the thieves. They stole my car five days ago.

7. The students have great difficulty in understanding each other. They don't have a common language

8. The customer asked to see the manager. He complained about the service.

9. The man was  an experienced mechanic. I sent for him to repair my motorbike. 

10. The boy has just gone out. Do you know him?