A portfolio which lies below the efficient frontier is described as________________.

The correct answer is: D. dominated.

A portfolio that lies below the efficient frontier is dominated by another portfolio. This means that the other portfolio has a higher expected return for the same level of risk, or a lower level of risk for the same expected return.

A portfolio that lies on the efficient frontier is said to be optimal, because it represents the best possible trade-off between risk and return.

A portfolio that lies above the efficient frontier is said to be unattainable, because it is not possible to achieve a higher expected return without also taking on more risk.

I hope this helps!