C选项如何理解

问题如下：

Park confirms with Kroll that the committee has historically used a traditional approach to define the opportunity set based on distinct macroeconomic regimes, and she proposes that a risk-based approach might be a better method. Although the traditional approach is relatively powerful for its ability to handle liquidity and manager selection issues compared to a risk-based approach, they both acknowledge that a number of limitations are associated with the existing approach.

A limitation of the existing approach used by the committee to define the opportunity set is that it:

选项：

A.

is difficult to communicate.

B.

overestimates the portfolio diversification.

C.

is sensitive to the historical look-back period.

解释：

B is correct. A traditional approach has been used to define the opportunity set based on different macroeconomic conditions. The primary limitations of traditional approaches are that they overestimate the portfolio diversification and obscure the primary drivers of risk.