$1.$ The Capital Asset Pricing Model:

$($a$)$ has serious flaws because of its underlying complexity.

$($b$)$ measures the relevant risk of a security and shows the relationship between risk and expected return.

$($c$)$ was developed by Markowitz in the $1930$s$.$

$($d$)$ discounts almost all of Markowitz's portfolio theory.

$($e$)$ None of the above