Explanation:

- Option 1: has perfect information

- In a perfectly competitive market, all firms have access to all necessary information, but this does not impact the shape of the revenue curve.

- Option 2: wants to maximize its profits

- All firms, whether competitive or not, aim to maximize profits. This desire does not directly influence the slope or shape of the revenue curve.

- Option 3: is a price taker

- In perfect competition, firms cannot set their own prices and must accept the market price. Hence, the total revenue curve is a straight line as revenue increases proportional to units sold.

- Option 4: faces constant returns to scale

- Constant returns to scale refer to a situation where increasing inputs leads to a proportional increase in output. This concept is more related to cost curves, not revenue curves.