Consider a portfolio manager whose mission is "to maximize annual returns through investments in the bonds of Industrial-Property REITS." which is the best opportunity cost investment for this manager? a) Blackstone's "Aggressive, Industrial REIT" ETF, which makes equity investments in REITS that manage industrial properties b. Blackstone's "Low-Volatility, Industrial REIT" Mutual Fund, which purchases the bonds of REITS that manage industrial properties c) Vanguards REIT Industry mutual fund, which makes money by purchasing the bonds of a large number of REITS of all types d) A mutual fund that makes loans to multi-family rental REITS.