In a portfolio, what does the Capital Allocation Line $($CAL$)$ represent when combined with a risk$-$free

asset?

a$.$ The set of portfolios that offer the best possible trade$-$off between risk and return.

b$.$ A line that represents the highest risk portfolios available.

c$.$ The relationship between the returns of the risk$-$free asset and the market portfolio.

d$.$ The line connecting all portfolios with the same level of risk.