For a Typical Natural Monopoly,what Is the Relationship Between Average

For a typical natural monopoly,what is the relationship between average total cost and marginal cost

A) average total cost is falling, and marginal cost is above average total cost
B) average total cost is falling, and marginal cost is below average total cost
C) average total cost is rising, and marginal cost is below average total cost
D) average total cost is rising, and marginal cost is above average total cost