Explanation

The correct answer is D - Any well-diversified portfolio may serve as the benchmark portfolio.

Detailed Analysis:

Why D is correct:

• In Arbitrage Pricing Theory (APT), the benchmark portfolio does not necessarily have to be the market portfolio
• APT allows for multiple factors that influence security returns, not just the market return
• Any well-diversified portfolio can serve as the benchmark portfolio as long as it is diversified across the relevant factors
• This flexibility is a key distinction between APT and the Capital Asset Pricing Model (CAPM)

Why other options are incorrect:

A is incorrect: The security market line (SML) shows the relationship between systematic risk (beta) and expected return, not portfolio variance (σ²).

B is incorrect: The SML has an upward slope, not downward, indicating that higher systematic risk is associated with higher expected returns.

C is incorrect: The x-axis intercept of the SML represents the risk-free rate, not the expected return on the market portfolio.

Key Concept:

Arbitrage Pricing Theory (APT) is a multi-factor asset pricing model that allows for multiple sources of systematic risk, making it more flexible than the single-factor CAPM. This flexibility extends to the choice of benchmark portfolios in APT applications.