Suppose you only consume food and clothing, and clothing is plotted on the vertical axis. Also, you purchase food at a fixed price (PF), but the price of clothing declines as you buy in larger quantities (i.e., quantity discounts). What does the budget line look like in this case?
选项：

A:The budget line is a straight line.
B:The budget line is now concave to (bows out from) the origin.
C:The budget line is now convex to (bows in toward) the origin.
D:The budget line will not be a straight line, but it may be concave or convex.