The correct answer is: A. two part tariff
A two-part tariff is a pricing strategy in which a consumer pays a fixed fee plus a per-unit charge for each unit of the good or service consumed. This type of tariff is often used by utilities, such as water and electricity companies, to recover the fixed costs of providing service.
A three-part tariff is a pricing strategy in which a consumer pays a fixed fee, a per-unit charge for each unit of the good or service consumed, and a per-period charge for each period of time that the good or service is used. This type of tariff is often used by telecommunications companies to recover the fixed costs of providing service, as well as the costs of connecting and maintaining the customer’s line.
A block rate tariff is a pricing strategy in which a consumer pays a different per-unit charge for each block of units of the good or service consumed. This type of tariff is often used by utilities to encourage consumers to use less energy.
Of the above options, a two-part tariff is the most efficient tariff for any type of consumer. This is because it allows the consumer to pay for the fixed costs of providing the good or service, as well as the variable costs of consumption. A three-part tariff is less efficient because it requires the consumer to pay for the fixed costs of providing the good or service, even if they do not consume any of the good or service. A block rate tariff is less efficient because it does not allow the consumer to pay for the variable costs of consumption, only the average variable costs of consumption.