Strongest evidence in support of the CAPM has come from demonstrating that

Group of answer choices

the market beta is equal to $1\mathrm{.}0.$

nonsystematic risk has significant explanatory power in estimating security returns.

the average return$-$beta relationship is highly significant.

the intercept in tests of the excess returns$-$beta relationship is exactly zero.

professional investors do not generally outperform market indexes, demonstrating that the market is efficient.