2010 Mock Exam Afternoon question

This might be a silly question. I am not getting my ahead around this One of the reasons I am uncomfortable using the CAPM is that it makes some restrictive assumptions 1. Investors pay no taxes, no transactions costs on trades 2. Investors have unique views on expected returns, variances and correlations of securiites 3. investors can borrow and lend at the same risk free of interest Which assumption of CAPM is most likely incorrect and why? I thought we need all the three assumptions

2 i think they have the same view not unique

investors have homogenous expectaions about returns etc