The operation of the Pony Express was a supreme achievement of physical endurance on the part of man and his ever faithful companion, the horse. The history of this organization should be a lasting monument to the physical sacrifice of man and beast in an effort to accomplish something worthwhile. Its history should be an enduring tribute to American courage and American organizing genius.

Which phrase from the fourth paragraph best expresses its main point?

A. A supreme achievement of physical endurance

B. Man and his ever faithful companion, the horse

C. The physical sacrifice of man and beast

D. Its history should be an enduring tribute