d不是也是降低预期收益率，为什么不选呢

问题如下：

An analyst concludes that the carbon density of Company A is increasing, how to adjust the valuation model due to the situation?

选项：

A.Give a premium of the company's PE ratio B.Increase the cost of capital C.Increase the book value of shareholders' equity D.Decrease the required rate of return

解释：

碳强度的增长说明该公司每单位收入所产生的碳排放增加，环境风险提高。因此需要调整估值模型以反映更低的估值。只用B选项可以使估值下降。