Problem: The sun was covered by a thick cloud all morning, but luckily, by the time the picnic started, *it* was out.
Are "it" and "The sun" the same?
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Answer: yes


Problem: Adam can't leave work here until Bob arrives to replace him. If Bob had left home for work on time, *he* would be here by this time.
Are "he" and "Adam" the same?
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Answer: no


Problem: Even before they reached town , they could hear a sound like corn popping. Dora asked what *it* was, and Dad said it was firecrackers.
Are "it" and "town" the same?
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Answer:
no