option vs impossibility

option and impossibility both are nouns.

Word	Noun	Adjective	Verb	Adverb
option	Yes	No	No	No
impossibility	Yes	No	No	No

As nouns, impossibility is a hyponym of option; that is, impossibility is a word with a more specific, narrower meaning than option:

option (noun)	impossibility (noun)
the act of choosing or selecting	an alternative that is not available
one of a number of things from which only one can be chosen	incapability of existing or occurring
the right to buy or sell property at an agreed price; the right is purchased and if it is not exercised by a stated date the money is forfeited