Under the Tobin Separation Theorem $($TST$),$ portfolio choice is separated into two stages:

$1-$ Find the efficient portfolio of risky assets;

$2-$ Find the optimum fractions to invest in the efficient portfolio of risky assets and in the risk$-$free asset.

In the first stage of the TST $-$ finding the efficient portfolio of risky assets $-$ how many different efficient portfolios are there?

Group of answer choices

One

Two

Three

An infinite number