What is an efficient$$portfolio$?$

A$.$An efficient portfolio is a portfolio that has the highest return in the economy.

An efficient portfolio is a portfolio that has the highest return in the economy.An$$efficient$$portfolio$$is$$a$$portfolio$$that$$has$$the$$highest$$return$$in$$the$$economy$.$

B$.$An efficient portfolio is any portfolio that only contains systematic risk long dash it contains no diversifiable risk.

An efficient portfolio is any portfolio that only contains systematic risk long dash it contains no diversifiable risk.An$$efficient$$portfolio$$is$$any$$portfolio$$that$$only$$contains$$systematic$$risk$$it$$contains$$no$$diversifiable$$risk$.$

C$.$An efficient portfolio is a portfolio that simultaneously has the highest return and the lowest volatility.

An efficient portfolio is a portfolio that simultaneously has the highest return and the lowest volatility.An$$efficient$$portfolio$$is$$a$$portfolio$$that$$simultaneously$$has$$the$$highest$$return$$and$$the$$lowest$$volatility$.$

D$.$An efficient portfolio is a portfolio that maximizes return at a relatively high cost.

An efficient portfolio is a portfolio that maximizes return at a relatively high cost.An$$efficient$$portfolio$$is$$a$$portfolio$$that$$maximizes$$return$$at$$a$$relatively$$high$$cost$.$