Q: Sentence (1) Change per unit volume.
Sentence (2) The centimetre is a unit of length.. Word: unit.
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A: the same meaning

Q: Sentence (1) He doesn't care about how / whether she comes.
Sentence (2) I don't care.. Word: care.
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A: the same meaning

Q: Sentence (1) I will work hard to improve my grades.
Sentence (2) They worked on the task.. Word: work.
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A:
the same meaning