Answer: They have invariably led to the implementation of a gold standard.

This question appears to be incomplete as only option A is provided. Based on historical financial crises since the Great Depression, common characteristics typically include: - **Asset price bubbles** and subsequent collapses - **Excessive leverage** in the financial system - **Credit booms** followed by sudden contractions - **Banking system vulnerabilities** and failures - **Contagion effects** across markets and institutions - **Regulatory failures** and gaps in oversight However, the implementation of a gold standard is NOT a common characteristic of financial crises since the Great Depression. In fact, most countries abandoned the gold standard during or after the Great Depression, and modern financial crises have occurred under fiat currency systems. Since the question only provides one option and it's historically inaccurate, this appears to be an incomplete question that would need additional options to be properly answered.

Author: Tanishq Prabhu