问题如下：
An industry with many firms and differentiated products and low barriers to entry is best characterized as:
选项：
A. perfect competition.
B. oligopoly.
C. monopolistic competition.
解释：
C is correct. Monopolistic competition is characterized by many firms, low barriers, differentiated products and some pricing power.
考点：垄断竞争
解析：垄断竞争具有企业多、壁垒低、产品差异化和一定的定价权等特点。
为什么不是完全竞争呢？
