Explanation:

- Total Cost (Option 1): The total cost curve in perfect competition generally curves upwards due to increasing costs, not a straight line.

- Marginal Cost (Option 2): Marginal cost can be upward or downward sloping and is typically not a straight line.

- Total Revenue (Option 3): The total revenue curve is not a straight line; it increases at a constant rate because it’s influenced by price multiplied by quantity.

- Marginal Revenue (Option 4): In perfect competition, marginal revenue is constant across different levels of output since firms can sell additional units at the market price, making the marginal revenue curve a straight line.