On a supply and demand graph, price will change when:A.there's a change in quantity demanded and a change in quantity supplied.B.either a change in quantity demanded or quantity supplied occurs.C.the quantity produced changes.D.the quantity purchased changes.E.either a change in demand or a change in supply occur.

The correct answer is E. On a supply and demand graph, price will change when either a change in demand or a change in supply occurs.

Here's why:

A. A change in quantity demanded and a change in quantity supplied: This is not necessarily true. A change in quantity demanded or supplied refers to movements along the demand or supply curve, which is caused by a change in the price of the good or service itself, not a cause of price change.

B. Either a change in quantity demanded or quantity supplied occurs: Similar to A, these changes are results of price changes, not causes.

C. The quantity produced changes: This could potentially affect price, but it's not a direct cause. The quantity produced is more related to the supply side of the equation, but it doesn't account for changes in demand.

D. The quantity purchased changes: This is similar to C, but on the demand side. It could potentially affect price, but it's not a direct cause.

E. Either a change in demand or a change in supply occur: This is correct. When the entire demand curve or supply curve shifts due to factors other than price (like income, population, tastes and preferences for demand, and cost of production, technology, or number of sellers for supply), it will cause a new equilibrium price, thus changing the price.