If government regulators want a natural monopolist to earn only zero economic profits, then they will set a price a. equal to average total cost (ATC). b. equal to marginal cost. c. such that marginal revenue equals marginal cost. d. none of the above

The answer to your q it is more

These tragedies are more likely to occur  when the benefit to the individual for using a bit more of the resource is greater than the associated cost.for example, a company may choose to dump all of its manufacture waste on the public lake (collective resource) because the cost of actually creating waste  management system would be higher compared to simply dumping them into the lake.