问题如下：
An investor should prefer a pooled investment vehicle to a separately managed account when she:
选项：
A. is cost sensitive.
B. focuses on tax efficiency.
C. requires clear legal ownership of assets.
解释：
A is correct.
Pooled investment vehicles are typically operated at a lower cost than separately managed accounts because operational costs can be spread among multiple investors. An investor who is focused on tax efficiency would prefer a separately managed account because a separate account allows the implementation of tax-efficient investing and trading strategies, and the investor pays taxes only on capital gains realized. If the investor requires clear legal ownership, they would prefer a separately managed account in which the investor owns the individual security directly.
