问题如下图：
选项：
A. 
B. 
C. 
解释：
感觉A.B都是对的，A哪错了？
NO.PZ2018062002000084 问题如下 Whiof the following is true regarng the performanof passive trang strategies in a semi-strong-form efficient market? A.Passive trang strategies woulearn abnormreturns. B.Passive trang strategies wouloutperform active trang strategies. C.Passive trang strategies woulunrperform active trang strategies. B is correct.For a funthapts active trang strategies, costs woulharto recover, so therefore, passive portfolio management shouloutperform active portfolio management on a consistent after-cost basis.考点Efficient CapitMarket AnIts Forms在半强有效市场中，active的策略也无法获得超额收益，但它比passive投资策略成本还高。所以passive投资策略会优于active投资策略。 为什么主动投资比被动投资的成本高？
NO.PZ2018062002000084 Passive trang strategies wouloutperform active trang strategies. Passive trang strategies woulunrperform active trang strategies. B is correct. For a funthapts active trang strategies, costs woulharto recover, so therefore, passive portfolio management shouloutperform active portfolio management on a consistent after-cost basis. 考点Efficient CapitMarket AnIts Forms 在半强有效市场中，active的策略也无法获得超额收益，但它比passive投资策略成本还高。所以passive投资策略会优于active投资策略。 老师，不是强有效下被动投资才强于主动投资吗？在半有效小，公开信息完全反映在股价上，但有些可以通过非公开信息获利（虽然方法不可取，但是如果能得到，也是通过非公开募内幕可以套利）。为什么在半强有效下就被动已经强于主动了？
Passive trang strategies wouloutperform active trang strategies. Passive trang strategies woulunrperform active trang strategies. B is correct. For a funthapts active trang strategies, costs woulharto recover, so therefore, passive portfolio management shouloutperform active portfolio management on a consistent after-cost basis. B说的是跑赢大盘吗，BC说的都在被动投资对吗
请问老师为什么是B不是C呢，能都一下意思吗，谢谢
