Industries that are made up of many competing producers,each selling a differentiated product,and whose firms earn zero economic profits in the long run are:

A) perfectly competitive.
B) monopolies.
C) oligopolies.
D) monopolistically competitive.

The description given in the question matches the characteristics of monopolistically competitive industries, in which multiple firms sell differentiated products, but there is still some degree of competition. In the long run, firms in monopolistically competitive industries earn zero economic profits due to the ease of entry and exit into the market. Therefore, choice D, monopolistically competitive, is the best answer.