The correct answer is: A. Variable cost
Contribution is the amount of revenue that is left over after variable costs have been paid. At break-even point, all of the revenue is used to pay for variable costs, so there is no contribution left over.
Variable costs are costs that change in proportion to the number of units produced or sold. For example, the cost of raw materials is a variable cost, because the more units you produce, the more raw materials you will need to buy.
Fixed costs are costs that do not change in proportion to the number of units produced or sold. For example, the rent on a factory is a fixed cost, because it does not matter how many units you produce, you will still have to pay the rent.
Total cost is the sum of variable costs and fixed costs.
Sales price is the price that a company charges for its products or services.
At break-even point, the company is making no profit and no loss. This means that the total revenue is equal to the total cost. The total cost is made up of variable costs and fixed costs. Therefore, at break-even point, the contribution is equal to the variable cost.