Concept:For a perfectly elastic demand curve, consumers will buy only at one fixed price.Explanation:When demand is perfectly elastic, the demand curve is horizontal at the current price.If a tax is imposed, the seller cannot pass it on to buyers through a higher price.Any price increase would cause quantity demanded to fall to zero.Therefore, the seller must absorb the entire tax burden to keep the price unchanged.Answer:The incidence of the tax falls entirely on the seller. (Option B)