Defining Relative Clauses

"This is the man who I love" = "This is the man I love"

Look at the example above. Here, the sentence is the same, with or without 'who'. Now look at the sentences below. If you think the sentence needs the word who/which, click 'yes'. If you think you don't need 'who/which', click 'no'.

I have a brother who is a doctor.
I live in a house which has six bedrooms.
I'm reading a book which I don't understand.
That's the dog which bit me.
I gave the money which I found to the police.
The chair which I sat on was broken.
The man who you met yesterday is very rich.
I shouted at the children who were playing in the garden.
I laughed at the joke which he told me.
I didn't understand the grammar which we studied yesterday.