Option 1 -> A downward sloping supply curve is not typical and does not represent zero elasticity.
Option 2 -> A horizontal supply curve represents perfectly elastic supply (infinite elasticity), not zero elasticity.
Option 3 -> An upward sloping supply curve represents normal supply with positive elasticity, not zero elasticity.
Option 4 -> A vertical supply curve represents perfectly inelastic supply where quantity supplied remains constant regardless of price changes.
Hence, Supply curve is vertical -> When price elasticity of supply equals zero, we have perfectly inelastic supply. This means quantity supplied does not respond to price changes at all (% change in quantity supplied = 0). Graphically, this is shown by a vertical supply curve where the same quantity is supplied at any price level. Examples include rare collectibles, land in a specific location, or goods with fixed supply in the short run. -> correct