Complex sentence: Clabber Girl is a brand of baking powder, baking soda and corn starch popular in the United States, manufactured by Hulman & Co., which also owns and operates the Indianapolis Motor Speedway and IndyCar, the sanctioning body for American open-wheel racing.
Split into simpler sentences: Clabber Girl is a brand of baking powder, baking soda, and corn starch popular in the United States. It is manufactured by Hulman & Co., which also owns and operates the Indianapolis Motor Speedway and IndyCar, the sanctioning body for American open-wheel racing.