下表为某科研人员对A、B、C、D四个生态系统中生物种类和数量的调查统计结果，根据表中数据分析推断，调节能力最强的生态系统是生态系统中生物种类和数量（单位：个）

An investment policy statement is important to the portfolio management process because it:（）

A. specifies allocations across assets and countries.

B. provides a clear understanding of the level of risk a client is willing to accept.

C. creates a record of the benchmark against which performance will be judged.