The correct answer is A. 0.
A straight-line demand curve meeting the two axes is a perfectly inelastic demand curve. This means that the quantity demanded does not change at all in response to a change in price. The price elasticity of demand is a measure of how responsive consumers are to changes in price. A perfectly inelastic demand curve has an elasticity of demand of 0. This means that a change in price will not cause any change in quantity demanded.
Option B is incorrect because a price elasticity of demand of 1 means that the quantity demanded changes in the same proportion as the price. This is not the case for a perfectly inelastic demand curve.
Option C is incorrect because a price elasticity of demand of 1.5 means that the quantity demanded changes in a greater proportion than the price. This is also not the case for a perfectly inelastic demand curve.
Option D is incorrect because a price elasticity of demand of 2 means that the quantity demanded changes in twice the proportion as the price. This is also not the case for a perfectly inelastic demand curve.