In the Added Perspective "The Corn Laws Controversy in 19th-Century

In the Added Perspective "The Corn Laws Controversy in 19th-Century England," the implication of David Ricardo's theory of differential rent is that

A) high rents were the main cause of high food prices in 19th-century England
B) price is rent determining; rent is not price determining
C) international trade ought to be restricted since it is instrumental in protecting landowners' rents
D) land rents are part of the cost of food production
E) differential land rents do not exist