Problem: Madonna fired her trainer because *she* couldn't stand her boyfriend.

Are "she" and "Madonna" the same?
Answer: yes

Problem: The delivery truck zoomed by the school bus because *it* was going so fast.

Are "it" and "the school bus" the same?
Answer: no

Problem: Emma's mother had died long ago, and *her* place had been taken by an excellent woman as governess.

Are "her" and "Emma" the same?
Answer: no

Problem: I couldn't put the pot on the shelf because *it* was too high.

Are "it" and "the shelf" the same?
Answer:
yes