Problem: The sack of potatoes had been placed below the bag of flour , so *it* had to be moved first.

Do "it" and "the bag of flour" mean the same thing?

Answer: yes

Problem: Billy cried because Toby wouldn't share *his* toy.

Do "his" and "Billy" mean the same thing?

Answer: no

Problem: When Tatyana reached the cabin, *her* mother was sleeping. She was careful not to disturb her , undressing and climbing back into her berth.

Do "her" and "Tatyana" mean the same thing?

Answer:
no