$3.$ The expected return of a portfolio of risky securities

a$.$ could be higher than the weighted average of the securities$\text{'}$ returns if the securities do not have perfect positive correlations.

b$.$ could be lower than the weighted average of the securities$\text{'}$ returns if the securities do not have perfect positive correlations.

c$.$ is the weighted average of the securities$\text{'}$ returns.

d$.$ is the weighted average of the securities$\text{'}$ returns only when if the securities have perfect positive correlations.

e$.$ is the weighted sum of the securities$\text{'}$ covariances.