Explanation

Option A is correct because:

• Extremely rare events can occur in structurally stable systems - This is a fundamental concept in risk management. Even when a system appears stable and follows established patterns, extreme tail events can still occur due to the inherent randomness and complexity of financial markets.

• The GARP quote acknowledges this reality - The statement mentions that risk events can be "very rare and extreme" OR "arise from unobserved structural changes." This means tail risk can come from either source: rare events in stable systems OR structural changes.

• Contrast with other options:

  • Option B is incorrect because we do have statistical techniques (extreme value theory, stress testing, scenario analysis) to analyze tail risk, though they have limitations.
  • Option C is incorrect because structural changes can significantly impact all forms of risk, including expected loss, unexpected loss, and especially tail risk.
  • Option D is incorrect because financial markets are fundamentally different from natural or mechanical systems due to human behavior, reflexivity, and the fact that market participants can change their behavior based on risk assessments.

Key Insight: Tail risk represents the possibility of extreme losses that occur with very low probability but severe consequences, and these can happen even in systems that appear fundamentally stable.