题目选项分析

Advertisement: Last year, Factorial Mutual Fund continued its strong record of investment performance. Investors who included Factorial Fund in their portfolios realized an average capital gain of 15% across all of their investment assets, nearly double the market return. Therefore, investors interested in high returns should consider adding Factorial Mutual Fund to their portfolios.

The claim in the advertisement above is based on which of the following assumptions?

【选项】A substantial part of the 15% portfolio appreciation was attributable to the returns of Factorial Fund and this level of fund's performance is likely to persist in the future.