C. A marketing ploy to help the candy industry.

An understandable and not totally incorrect answer. Shoppers this year are expected to spend $1.8 billion on candy, buy 50 million greeting cards and spend between $1 billion and $1.5 billion on costumes, according to the National Retail Foundation.

-- The correct answer is B.
A. A satanic holiday.
B. An ancient Celtic fire festival.