Butter is made by agitating cream to form a ____________ emulsion.

Butter is indeed made by agitating cream to form a water-in-oil emulsion. In the process of making butter, the fat molecules in cream are agitated, which causes them to clump together and separate from the liquid portion or buttermilk. This results in a mixture where the water content (in the form of buttermilk) is dispersed in the fat (the butter), characterizing it as a water-in-oil emulsion.

In a water-in-oil emulsion, the water droplets are dispersed in oil or fat, which is the defining trait of butter. This is different from an oil-in-water emulsion, where oil droplets are dispersed in water, which is what you would typically find in products like milk or mayonnaise. The other options, such as gas-in-liquid and gas-in-solid, do not apply to the process of butter production, as there is no significant gas phase present in butter. Therefore, the correct characterization of butter as a water-in-oil emulsion accurately reflects its composition and the physics involved in its formation.