一级Equity中关于industry analysis的问题 industry, analysis

christy931

"Which of the following industries is most likely to be considered to have the lowest barriers to entry?
A        Oil services.
B        Confections and candy.
C        Branded pharmaceuticals.

Solution: A is correct. The oil services industry has medium barriers to entry because a company with a high level of technological innovation could obtain a niche market in a specific area of expertise."
Institute, CFA. CFA Institute Level I 2014 Volume 5 Equity and Fixed Income. John Wiley & Sons P&T, 2013-07-12. VitalBook file.

完全无法理解为什么正确答案是A，甜食公司总比石油公司好建吧？？而且答案解释中也说石油公司has MEDIUM barriers to entry，那么为什么选A呢？

菜鸟一个，望各位耐心解答，拜谢！！