How and why did the economic relationship between great britain and its colonies changed after the french and indian war?

The French and Indian War changed this relationship by making it a great deal worse.  In fact, the war can be said to have led to the revolution.

First, the war took the French out of North America.  The colonists no longer had to fear being taken by France if they were to break free from Britain.

Second and more importantly, the war cost a huge amount of money. The British felt that the colonies should pay some part of that sum.  The colonists had not been taxed as heavily as the people in Britain itself and the British government felt this should change.  The taxes that the British then imposed on the colonies were the major cause of the discontent that led to the Revolutionary War.

just finished this it is b. centrifugal force

yup! you are correct it is b.