What fundamental principles do generally accepted investment theories involve?

The correct choice reflects the essence of generally accepted investment theories, which focus on the belief that investment decisions should be grounded in sound reasoning and analysis. Such theories emphasize that investors should adopt approaches based on an understanding of market behaviors, risk-return trade-offs, and long-term goals. By advocating for appropriate and rational investing strategies, these theories encourage investors to consider various factors, including diversification, asset allocation, and time horizons. This leads to more informed and balanced investment decisions.

The other options do not align with the core principles of established investment theories. For instance, the idea of eliminating all risks is not feasible, as some level of risk is inherent in nearly all investments. Categorizing investments by expense ratios, while useful, does not encapsulate the comprehensive nature of investment theories that address how different assets relate and perform over time. Likewise, focusing exclusively on index funds overlooks the broader spectrum of investment opportunities and strategies available to investors, which could lead to missed chances for enhanced returns through diversification and active management.