Problem: Then he took a piece of iron the shape of the horse horse's foot , and clapped *it* on, and drove some nails through the shoe quite into its hoof, so that the shoe was firmly on

Are "it" and "piece of iron" the same?
Answer: yes

Problem: Sir Clifford wants me to find him a new groom , about twenty or twenty-one, who knows his business. *His* old coachman is getting feeble, and he wants a man to work with him and get into his ways, who would be able, when the old man was pensioned off, to step into his place.

Are "His" and "new groom" the same?
Answer: no

Problem: Many people start to read Paul's books and can't put them down. *They* are gripped because Paul writes so well.

Are "They" and "Paul's books" the same?
Answer: no

Problem: The mothers of Arthur and Celeste have come to the town to fetch them. *They* are very happy to have them back, but they scold them just the same because they ran away.

Are "They" and "mothers" the same?
Answer:
yes