Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.

Q: molar mass is the mass of a substance that has 6.022 10 atoms (avogadro's number).

A: molar mass
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Q: georges loinger (29 august 1910 28 december 2018) was a french resistance fighter during world war ii.

A: georges loinger
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Q: the book of numbers in the bible is the fourth book in the old testament.

A:
book of numbers
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