这题怎么理解？

问题如下：

At the portfolio management level, ESG integration is appropriate for which of the following investment strategies?

选项：

A.Systematic only

B.Discretionary only

C.Both systematic and discretionary

解释：

C. Correct because ESG integration should be considered in light of two different investment strategies: Discretionary ESG investment strategies most commonly take the form of a fundamental portfolio approach. A portfolio manager would work to complement bottom-up financial analysis alongside the consideration of ESG factors to reinforce the investment thesis of a particular holding. The portfolio manager would then work to understand the aggregate risk at the portfolio level across all factors to understand correlation and event risks, and potential shocks to the portfolio. Quantitative investment strategies are, broadly speaking, rules-based approaches employing the statistical application of financial and/or non-financial factors to drive securities selection. Quantitative strategies generally seek to minimise the higher costs associated with discretionary active management. Where discretionary strategies often focus on depth within a portfolio, manifested through a portfolio of few, more concentrated holdings, quantitative strategies focus on breadth, using a much larger portfolio of holdings to target risk and volatility-adjusted returns.