If the coefficient of price elasticity of demand of a product is zero, then its demand curve will be

If the coefficient of price elasticity of demand of a product is zero, it means that the demand for the product is perfectly inelastic. This implies that a change in price will not lead to any change in the quantity demanded of the product. In other words, regardless of the price of the product, the quantity demanded will remain the same. Therefore, the demand curve will be a vertical line parallel to the quantity axis. This is because changes in price will not cause any change in the quantity demanded, and hence the demand curve will not slope. So, the answer is "parallel to the quantity axis."