As long as the average variable cost of production is falling, _____.

the marginal cost will also be falling
marginal cost will be less than average variable cost
the average total cost will be equal to zero
the average fixed cost will be constant

Explanation
The average-variable relationship is that so long as the average value is falling, the marginal value will be lower than the average value. Hence, when average variable costs are falling, marginal costs will be lower than average variable costs.