If a Production Possibilities Curve for Books and Magazines Is

If a production possibilities curve for books and magazines is a straight line,then the

A) opportunity cost of increasing book production stays constant regardless of the quantity produced.
B) opportunity cost of increasing book production continues to decline as total production increases.
C) opportunity cost of increasing book production is independent of the shape of the curve.
D) opportunity cost of increasing book production continues to increase as total production increases.