Which of the following is$/$are true:

I. The y$-$axis measures rates of return and the x$-$axis measures levels of risk

II$.$ Risk is generally considered to be the variance of market prices

III. The risk$-$free rate is located on the intercept of the CML to the x$-$axis

IV$.$ The CML takes into consideration buying investments on margin

a$.$ All are true.

b$.$ None are true.

c$.$ All but IV are true.

d$.$ Only I and III are true.

e$.$ Only I, II$,$ and IV are true.