support for your justification

“Diversification” Please respond to the following:

Justify whether the standard deviation or covariance is the most significant measurement when adding a risky asset to an already highly risky portfolio. Provide support for your justification.

An investor ponders various allocations to the optimal risky portfolio and risk-free T-bills to construct his complete portfolio. Predict two ways that the Sharpe ratio of the complete portfolio could be affected by this choice. Support your prediction with examples.