Answer:
downward sloping; horizontal line; individual demand; large number of competitors
Explanation:
A monopoly firm is a single producer in the market with no close substitutes. It is a price maker and thus faces a downward-sloping demand curve.
A perfectly competitive firm, however, faces a horizontal line demand curve as it is a price taker. There is a large number of firms in a perfectly competitive market. These firms produce homogenous products. So no single firm can affect the price level.
In monopoly, the individual and market demand curve is the same as the firm is the only producer in the market. While, the market demand curve in a perfectly competitive market is downward sloping, as the firm is operating with a large number of competitors.