问题如下：
There are three approaches to attribution analysis: the return-based, holdings-based, and transaction-based approaches. An investment committee would like to choose from the above attribution method meets below descriptions: (1) apply the attribution method that uses only each fund’s total portfolio returns over the last 12 months to identify return-generating components of the investment process and (2) include the impact of specific active investment decisions and the attribution effects of allocation and security selection in the report.
Compared to other two methods, the method requested by the committee:
选项：
A.is the least accurate.
B.uses the underlying holdings of the actual portfolio.
C.is the most difficult and time consuming to implement.
解释：
A is correct.
The committee described a return-based attribution, which is the least accurate of the three approaches (the return-based, holdings-based, transaction-based approaches). Return-based attribution uses only the total portfolio returns over a period to identify the components of the investment process that have generated the returns.
(2) include the impact of specific active investment decisions and the attribution effects of allocation and security selection in the report.
关于这一点为什么也是return based 的特点那？
