The capital asset pricing model helps you to understand the importance of diversification. Investors who follow the CAPM model choose assets that fall on the capital market line by lending or borrowing at the risk-free rate. (M1 Finance)

The Capital Asset Pricing Model (CAPM) is based on assumptions. First, the model assumes that a riskier asset will yield a higher return. But this is not necessarily true (The strategic CFO)

The capital asset pricing model (CAPM) builds on the Markowitz mean–variance-efficiency model in which risk-averse investors with a one-period horizon care only about expected returns and the variance of returns (risk). (CFA Institute)