Variable cost varies at different level of output, this implies that when the output of a particular firm is at zero, the variable cost will be zero and when there is increase in production of output, there will also be a corresponding increase in the variable cost.
Fixed cost is wrong because it remains constant irrespective of the change in the level of production. The marginal cost interact only with the variable cost, it is the cost added by producing one additional unit of a product.
The average cost is total cost of production of a commodity expose by a firm divided by the number of output.
Wrong answer!! Variable cost absolutely increases with the increase in production, while Marginal Cost often decreases with the increase in production due to cost savings, efficiency of scale.
The designated ans "Marginal Cost" is absolutely WRONG. Very often, marginal cost of an item produced is decreased with an increase in production. It is the variable portion of the total cost that always increases with increase in production.