单选题 Generally speaking, the factor that best explains a portfolio's level of return and variation in return over time can be explained by: A. target asset allocation decision. B. investment manager's skill with respect to market timing. C. investment manager's skill with respect to security selection.

【正确答案】 A

【答案解析】Several studies support the idea that approximately 90 percent of a portfolio's returns can be explained by its target asset allocations.