Concept:Perfectly inelastic demand means quantity demanded does not change when the price changes.Explanation:In this case, the demand curve is perfectly vertical.When a tax is imposed, the producer tries to shift the tax burden to the buyer.Since buyers continue to purchase the same quantity even at a higher price, the full burden of the tax falls on the consumer.Thus, the producer can pass the entire tax to the consumer without losing sales.Answer:B. is borne only by the consumer