What word do I look to in this sentence to determine that Hvilken should receive an en ending?
"Periode", it always takes the gender/plurality of the noun it's asking about, so "Hvilket hus bor du i?" = "Which house do you live in?" or "Hvilke bøger har du læst?" = "Which books have you read?"
Wrong answer in danish. The right answer is hvilken historiske periode er det or hvilken periode er det historisk
Why is it "historiske"? Is "hvilken" considered as a determinant here, so that we need to use the det. form of the adjective?