In Applying the CAPM to Estimate the Cost of Equity $\beta$

In applying the CAPM to estimate the cost of equity capital, which of the following elements is not subject to dispute or controversy?

A) Expected rate of return on the market, rM.
B) The share's beta coefficient, ( $\beta$ ) . i.
C) Risk-free rate, rRF.
D) Market risk premium (MRP) .
E) All of the above are subject to dispute.