Efficiency Comes About in Perfectly Competitive Free Markets When

Efficiency comes about in perfectly competitive free markets when:

A) Firms are motivated to invest resources in industries with a high consumer demand and move away from industries where demand is low.
B) Firms are encouraged firms to minimize the resources they consume to produce a commodity and to use the most efficient technologies.
C) Commodities are distributed among buyers such that buyers receive the most satisfying commodities they can purchase, given what is available to them and the amount they have to spend.
D) All the above
E) A & B