问题如下：
Dewey asks Sardar to perform a bottom-up style analysis of the Purity Fund based on the aggregation of attributes from individual stocks in the portfolio. Dewey plans to include the results of this style analysis in a profle he is preparing for the fund. The analysis performed by Sardar on the Purity Fund can be best described as being based on:
选项：
A. a holdings-based approach
B. manager self-identifcation
C. a returns-based style analysis
解释：
A is correct. Dewey asks Sardar to perform a bottom-up style analysis of the Purity Fund based on the aggregation of attributes from individual stocks in the portfolio, which describes a holdings-based approach to style analysis. The overall equity investment style is an aggregation of attributes from individual stocks in the portfolio, weighted by their positions.
