cost effective 是 enhanced indexing 嘛，“pure indexing”是 minimum cost 不是 cost effective是嘛

问题如下：

To meet both of Trey’s guidelines for the pension’s bond fund investment, Serena should recommend:

选项：

A.

pure indexing.

B.

enhanced indexing.

C.

active management.

解释：

B is correct. Low tracking error requires an indexing approach. A pure indexing approach for a broadly diversified bond index would be extremely costly because it requires purchasing all the constituent securities in the index. A more efficient and cost-effective way to track the index is an enhanced indexing strategy, whereby Serena would purchase fewer securities than the index but would match primary risk factors reflected in the index. Closely matching these risk factors could provide low tracking error.