Problem: The foxes are getting in at night and attacking the chickens . I shall have to guard *them* .

Are "them" and "the chickens" the same?
Answer: yes

Problem: I asked Dave to get me my sweater from the other side of the yacht . While he was gone, I rested my arm on the rail over there and suddenly *it* gave way.

Are "it" and "arm" the same?
Answer: no

Problem: Sara borrowed the book from the library because she needs *it* for an article she is working on. She reads it when she gets home from work.

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

Problem: Tom said "Check" to Ralph as he moved *his* bishop.

Are "his" and "Tom" the same?
Answer:
yes