Graph the of portfolio $1$ to $8$ against their standard deviation $($ STD is on the horizontal axis.$)$ The graph shows that: A$)$ to attain a higher expected return the investor has to tolerate higher risk B$)$ there is a positive linear relationship between expected return and risk C$)$ the mean$-$return compensations of equal$-$std$-$ncrements decline as we target higher and higher risk D$)$ answers $1$ and $3$ are correct E$)$ answers $1$ and $2$ are correct