Why is a fixed cost curve horizontal?

Why is a fixed cost curve horizontal?

1. Provide some examples of unavoidable fixed costs. How are these related to sunk costs? Describe why a firm should not consider sunk costs when making decisions.
2. Describe the relationship between fixed, variable, and total costs.
3. Why is a fixed cost curve horizontal? Why does a variable cost curve have a positive slope?

Why is a fixed cost curve horizontal?