Final answer:
The statement is false; the key difference is not the lack of free entry but rather the presence of barriers to entry that gives a monopoly its price-setting power, as opposed to monopolistic or perfect competition.
Step-by-step explanation:
The assertion that the lack of free entry is the key to having the ability to set price in comparing monopolistic competition to perfect competition is false. In a perfectly competitive market, there are no barriers to entry or exit, allowing firms to enter freely and compete, which inhibits any single firm from setting the price; they are price takers.
On the other hand, monopolistic competition presents a market structure where many firms sell products that are similar but not identical, and while there may be some barriers to entry, they are not insurmountable.
Monopolies, which are characterized by significant barriers to entry, have the power to set prices because they face no significant competition. This is different from both monopolistic and perfectly competitive markets where firms have less control over the prices due to the presence of competitors.