Assuming a Product Can Be Manufactured Competitively Without Any Externalities

Assuming a product can be manufactured competitively without any externalities at an efficient quantity of 1,000 units and an efficient price of $100.00 per unit, what efficient quantity-price combination would be consistent with a negative externality?

A) 1,000 units, $95.00 per unit price.
B) 950 units, $102.00 per unit price.
C) 900 units, $90.00 per unit price.
D) 1,100 units, $105 per unit price.