BBC ESL-Subject&Verb Agreement

I entered BBC ESL and  studied subject&verb agreement. There are 8 questions and I answered 6 right answer.

-The media have reported the death of the president.
-Some people think that maths is really difficult.
-Diabetes is on the increase in the developed world.
(Maths is not plural. just a word that is ended 's')
-The children were told not to jump in the furniture.
(Children's singular is child)
-The orchestra was taken to the hotel by coach.
-I'm sure my team is going to win the match.

And this is the right answer of my error.
Everyone who was injured in the accident was taken to hospital.
-> 'Everyone' have a plural meaning, but take singular verbs.
The police are forbidden by law to go on strike.
-> 'police' is a word that is collective nouns. This can be not only singular, but also plural. 

And..My last class is coming..I'm so sad..