问题如下：
In their later work, Fama and French (2015) added two more factors. Which of the following is a basis for one of these new risk factors?
选项：
A.Operating profitability
Current assets to current liabilities
Net profit to total assets
Last month performance
解释：
A is correct. Operating profitability
Fama and French extended the model in 2015 by suggesting two additional factors:
1. RMW, which is the difference between the returns of companies with high (robust) and low (weak) operating profitability; and
2. CMA, which is the difference between the returns of companies that invest conservatively and those that invest aggressively.
老师上课讲的是新加的模型和HML有密切相关性。HML是基于B/M比率来的。请问为什么可以认为operation profitability和B/M有关呢？
