Matt Taylor Is One of the Fishermen Who Returns to the Dock

Matt Taylor is one of the fishermen who returns to the dock at the end of a fishing day with 720 fish in his boat. He and 40 other fishermen crowd the dock with their fish supplies while hundreds of people, eager to buy fish, make their demands felt on themarket. Matt knows that for the current fishing day

A) price cannot change
B) the market-day supply curve is vertical
C) the market-day demand curve is vertical
D) quantity demanded is fixed
E) his short-run supply curve is upward sloping