When a negative externality exists, the marginal social cost is always higher than the marginal private cost. So, the correct answer is option A the private marginal costs are less than social marginal costs.
When the manufacturing process has a negative impact on unconnected third parties, this is referred to as a negative production externality. For instance, manufacturing facilities contribute to noise and air pollution throughout the production process.
The marginal social cost and the marginal private cost are no longer equal when a market has negative production externalities. As a result, the supply curve (which indicates the marginal private cost) does not accurately reflect the marginal societal cost and the social cost is instead larger due to the externality's per-unit cost.
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