A little confused on how to go about answering the question! Help please!

36. Allen Marko, CFA, is analyzing the diversification benefits available from investing in three equity funds. He is basing his analysis on monthly returns for the three funds and an appropriate market index over the past twenty years. He feels that there is no reason that the past performance should not carry forward into the future. Treasury bills currently pay 5%. Table 1: Expected Returns, Variances, and Covariance for Funds A, B, & C Equity Fund A Equity Fund B Equity Fund C 9% 0.0196 Average Return! 12% 0.0256 8% 0.0172 Variance Correlation of A & B is 0.50 Correlation of A & C is 0.38 Correlation of B & C is 0.85 Marko has also obtained information about a fourth fund, Fund D. He does not have any information regarding the covariance of Fund D with Funds A, B, and C. The average return and variance for fund D are 10% and 0.018, respectively. The beta of Fund D is 0.714. If Marko had to choose to form a portfolio using only T-bills and one of the four funds, which should he choose? (4 points)