A broker was sanctioned for unsuitable recommendations and excessive trading involving three accounts under his care. These clients were unsophisticated, inexperienced individual investors with limited means. According to CFA Institute Standard Ⅲ (C) , Suitability, which of the following is least likely to be considered a relevant factor in determining the appropriateness and suitability of investment recommendations or actions for each portfolio or client （）
A. Best interests of the investment professional.
B. Basic characteristics of the total portfolio.
C. Basic characteristics of the investment involved.