The farmer had to remove a large thorn from the horse's hindquarters

a. chest
b. hoof
c. front leg
d. rear leg

Rear Leg matches hindquarters

Explanation:

The hindquarters of a horse are in their back physiognomy, the area that in anatomy is called croup and that connects with the rear legs (or back legs), therefore in the sentence given "The farmer had to remove a large thorn from the horse's hindquarters " they are talking about the rear leg of the horses.

51. i'm

52 idk

53. just

the chivalry's most valued code is morality