The correct answer is: A. capital asset pricing model (CAPM)
The CAPM is a model that describes the relationship between risk and expected return for assets, and is widely used in finance to help investors make decisions about asset allocation. The CAPM states that the expected return of an asset is equal to the risk-free rate of return plus a risk premium that is proportional to the beta of the asset. The beta of an asset is a measure of its volatility relative to the market, and a higher beta indicates that the asset is more volatile and therefore has a higher risk premium.
The CAPM is a useful tool for investors because it provides a framework for thinking about risk and return. However, it is important to note that the CAPM is just a model, and it is not always accurate. The CAPM is based on a number of assumptions, and if these assumptions are not met, then the CAPM may not be accurate.
The other options are incorrect because they are not models that describe the relationship between risk and expected return. Option B, portfolio asset pricing model, is a model that describes the relationship between risk and return for a portfolio of assets. Option C, asset market pricing model, is a general term for any model that describes the relationship between risk and return for assets. Option D, portfolio pricing model, is a general term for any model that describes the pricing of a portfolio of assets.