Final answer:
Tying sales happen when a customer is required to buy one product only if the customer also buys a second product. This practice restricts the customer's choice and is viewed as anti-competitive.
Step-by-step explanation:
Tying sales happen when a customer is required to buy one product only if the customer also buys a second product. Tying sales are controversial because they force consumers to purchase a product that they may not actually want or need. For example, if a popular DVD is being sold with a requirement to also purchase a certain portable TV model, this would be a tying sale. This practice restricts the customer from having the option to select a different portable TV model, which may be more preferable or affordable. Tying sales are viewed as anti-competitive and can limit consumer choice.