A portfolio consisting of two risky securities can be made risk-less
i.e, σp = 0, if:

A portfolio consisting of two risky securities can be made risk-less (i.e., σp = 0) if: The securities are perfectly negatively correlated. When two securities in a portfolio are perfectly negatively correlated, it means that they move in exact opposite directions. When one security's value goes up, the other's value goes down by the same amount, and vice versa. By combining two perfectly negatively correlated securities in a portfolio, the fluctuations cancel each other out, resulting in a risk-less portfolio. This is because any gain in one security offsets the loss in the other, and the overall portfolio value remains constant regardless of market movements.