Concept:Joint supply occurs when one production process yields two or more related products.Explanation:Beef and hides are both obtained from the same animal, cattle.If more cattle are raised for beef, hides are also produced as a natural by-product.Therefore, an increase in the supply of beef will automatically increase the supply of hides.This relationship indicates that beef and hides are produced together from a single source.Hence, they are in joint supply.Answer:B. joint supply