Seasonal Adjustments to GDP Occur Because

Seasonal adjustments to GDP occur because:

A) the demand for products varies year by year, which causes fluctuations in expenditures.
B) seasonal variations in temperature affect price levels during each year, which causes GDP to vary.
C) output in many industries varies by season of the year, which makes the quarterly GDP measures fluctuate.
D) the stages of the business cycle are referred to as seasons, which causes year-to-year variations.