A Horse Pulls a Cart with Force $\overrightarrow { \mathrm { F } }$

A horse pulls a cart with force $\overrightarrow { \mathrm { F } }$ As a result of this force the cart accelerates with constant acceleration.The magnitude of the force that the cart exerts on the horse

A) is zero newtons.
B) is equal to the magnitude of $\overrightarrow { \mathrm { F } }$
C) is less than the magnitude of $\overrightarrow { \mathrm { F } }$
D) is greater than the magnitude of $\overrightarrow { \mathrm { F } }$
E) cannot be determined without knowing the mass of the horse.