Q: Sentence (1) That mountain is solid rock.
Sentence (2) He threw a rock at me.. Word: rock.
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A: different meanings

Q: Sentence (1) He needs to regain her trust if he is ever going to win her back.
Sentence (2) He betrayed their trust.. Word: trust.
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A: different meanings

Q: Sentence (1) Simply an identity element if both are true.
Sentence (2) A left identity if I * x = x for any x in the structure.. Word: identity.
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A:
the same meaning