专家您好请详细解释一下这题，不是很理解这题，且讲义依据是什么，谢谢

问题如下：

For which of the following types of ESG activity would it be easiest to analyze the impact on a portfolio's performance?

选项：

A.Exclusion of an industrial sector such as tobacco

B.Voting for shareholder proposals relating to climate change

C.Active engagement on issues of health and safety and workers' rights

解释：

A is correctbecause the attribution of returns to ESG factors is challenging, not leastbecause of the significant range of investment approaches that are included inthe broad realm of ESG investing. It is relatively easy to assess theperformance drag or enhancement that comes from excluding an industrial sector(such as tobacco), but it is hard to demonstrate the value added by a programof engagement, particularly given the timescales usually required forengagement programs to reach positive outcomes.

B is incorrectbecause the attribution of returns to ESG factors is challenging, not leastbecause of the significant range of investment approaches that are included inthe broad realm of ESG investing. It is relatively easy to assess theperformance drag or enhancement that comes from excluding an industrial sector(such as tobacco), but it is hard to demonstrate the value added by a programof engagement, particularly given the timescales usually required forengagement programs to reach positive outcomes.

C is incorrectbecause the attribution of returns to ESG factors is challenging, not leastbecause of the significant range of investment approaches that are included inthe broad realm of ESG investing. It is relatively easy to assess theperformance drag or enhancement that comes from excluding an industrial sector(such as tobacco), but it is hard to demonstrate the value added by a programof engagement, particularly given the timescales usually required forengagement programs to reach positive outcomes.