What does 'keep your head' mean?

Which is the best paraphrase of the passage? a.)it’s always cloudy where the men of winter live. b.)it’s always misty where the men of winter live. c.)it’s always dark where the men of winter live. d.)it’s always sunny where the men of winter live. read the passage from the odyssey - elpenor. by night our ship ran onward toward the ocean's bourne, the realm and region of the men of winter, hidden in mist and cloud. never the flaming eye of helios lights on those men at morning, when he climbs the sky of stars, nor in descending earthward out of heaven; ruinous night being rove over those wretches.