Question

1. Do/Does chocolate make you happier?
2. Economics is/are difficult.
3.Mumps cause/causes high temperature.
4. His knowledge of French is/are rather good.
5. Evidence was/were found by Mr. Black.
6. Where is/are my pyjamas?
7.The police has/have arrested the burglar.
8. Do you believe that the jury was/were given money?

Answer 1

1. Does chocolate make you happier?
2. Economics is difficult. 
3.Mumps causes high temperature.
4. His knowledge of French is rather good.
5. Evidence were found by Mr. Black.
6. Where is my pyjamas? 
7.The police has arrested the burglar.
8. Do you believe that the jury was given money?