prepositions + change

Money isn't the solution (a)   every problem.

There has been an increase (a)   the amount of traffic on this road.

Everything can be explained. There is a reason (a)   everything.

When Paul left home, his attitude (a)   his parents was strange.

There has been a sharp rise (a)   property prices in the past few years.

What was her reaction (a)   the news?

The company rejected the workers' demands ___ a rise ___ pay.

(a)  

What was the answer (a)   question 3?