Two analogies that signify affordances are given in the form "A : B. C : ?". Affordance is the possibility of an action being done on an object, for example book is an affordance of writing. The phrase "A : B" implies that B is an affordance of A. Your task is to replace the question mark (?) with the appropriate affordance of the given action C, following the "A : B" relation. Your answer should be a single object without further explanation.

Q: swing : sword. open : ?

A: door
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Q: open : door. sing : ?

A: song
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Q: climb : tree. cure : ?

A:
disease
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