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: the usl w-league is a national women's soccer league.

A: w-league
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Q: a sandwich panel is a kind of composite material, which is usually made of two components: a small outside layer (which is the same on both sides), and an inside layer, which is used to get certain properties, for example insulation or fire resistance.

A: sandwich panel
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Q: a candela is the si base unit of luminous intensity.

A:
candela
****