You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

Category: REMEMBRANCE OF THINGS "CAST" 
Clue: Hey, baby, you a Gemini?  These twin brothers of Helen of Troy are, literally
castor & pollux

Category: TOUGH BODIES OF WATER 
Clue: Finland's Aland Islands lie at the southern edge of this gulf
the gulf of bothnia

Category: SCIENC"E" 
Clue: These solar seasonal events occur in March & September

equinox