'A Competitive Market Achieves Economic Efficiency by Maximising the Sum

Multiple Choice

'A competitive market achieves economic efficiency by maximising the sum of consumer surplus and producer surplus.' This statement

A) is true only if there are positive externalities in production in the market.
B) is true only if there are no negative externalities in the market.
C) is true only if there are no positive or negative externalities in the market.
D) is true in theory, but economic efficiency cannot be achieved in a real market.