One Reason Supply Curves Have an Upward Slope Is Because

One reason supply curves have an upward slope is because

A) a higher price brings a greater profit, so firms want to sell more of that good.
B) increased supply will require increased technology.
C) to have more of the good supplied requires more firms to open.
D) people will pay a higher price when less is supplied.
E) None of the above answers is correct because supply curves have a downward slope.