Final answer:
In monopolistic competition, advertising can reduce search and information costs for consumers, and while there are some barriers to entry, they are not as pronounced as in monopoly or oligopoly markets.
Step-by-step explanation:
Monopolistic competition is a market structure that shares certain characteristics with perfect competition but also has some distinct differences. One true statement about monopolistic competition is that advertising can decrease search and information costs, making it easier for consumers to find and learn about different products. This is in contrast to a perfectly competitive market, where products are homogeneous, and there typically isn't a need for advertising. Although monopolistically competitive markets have some barriers to entry and exit, they are still relatively low compared to monopoly or oligopoly markets. Furthermore, excess capacity in monopolistic competition means that firms produce at an output level where average total cost is not minimized, which occurs when price lies on the downward-sloping portion of the average cost curve, not at its bottom.