The correct answer is D. efficient portfolios.
An efficient portfolio is a portfolio that maximizes expected return for a given level of risk, or minimizes risk for a given level of expected return. In other words, an efficient portfolio is the best possible portfolio for a given investor’s risk tolerance.
Risky portfolios are portfolios that have a higher level of risk than other portfolios. These portfolios may offer the potential for higher returns, but they also come with a greater risk of loss.
Behavior portfolios are portfolios that are based on the investor’s behavior, rather than on traditional investment principles. These portfolios may be more or less risky than other portfolios, depending on the investor’s personality and investment goals.
Inefficient portfolios are portfolios that do not maximize expected return for a given level of risk, or minimize risk for a given level of expected return. These portfolios are not the best possible portfolios for a given investor’s risk tolerance.