What substance is NOT one of the three products purchased by the government to stabilize milk prices?

The correct choice indicates that sour cream is not among the three products purchased by the government to stabilize milk prices. The government typically engages in purchasing cheese, butter, and nonfat dry milk as part of the Dairy Price Support Program, which aims to stabilize and support the dairy market by maintaining a price floor for these key dairy products.

Sour cream, although a dairy product, does not play the same role in price stabilization as the other three. This is primarily due to factors such as its lower production scale compared to cheese, butter, and nonfat dry milk, and it does not have the same level of inclusion in government support mechanisms aimed at impacting wholesale milk prices directly. The focus of government purchases is generally on products that can be stored for longer periods and have a more substantial impact on the market balance.