Last Summer,Casey Took Fresh Vegetables to Sell at the Farmer's

Last summer,Casey took fresh vegetables to sell at the Farmer's Market,but this year,Casey did not plant any vegetables and went to work at the local bank.
Refer to the information above.If Casey's decision to change careers did not change the market price for vegetables at the Farmers' Market,it is because:

A) demand for vegetables did not change.
B) the Farmers' Market attracts a large number of vegetable farmers.
C) demand for vegetables increased this year.
D) the price is set by a regulatory body.