Concept:Perfectly elastic supply means the quantity supplied can change without any change in price.
Explanation:A perfectly elastic supply curve is drawn as a horizontal straight line at a given price.
This shows that producers are willing to supply any quantity at that exact price.
If the price falls even slightly, quantity supplied would drop to zero.
The horizontal shape indicates that price remains constant while quantity supplied varies freely.
This is a theoretical extreme case and does not actually exist in real markets.
Therefore, the supply curve is horizontal, not vertical, downward-sloping, or upward-sloping.
Answer:B. is horizontal