Look at these examples of relative clauses:
We can combine the two sentances,
*Notice that we use who,/that, or which/that to substitute the subject of the second sentance.
I like a woman. She lives next door. :
I like the woman who/that lives next door.
She has a son. He is a doctor:
She has a son who / that is a doctor.
We bought a house. The house is 200 years old:
We bought a house which / that is 200 years old.
Now answer the following exercises: