Among the provided investment options, which one is considered a higher risk vehicle?

Penny stocks are considered a higher risk investment vehicle primarily due to their low market capitalization, low liquidity, and the fact that they are often traded on over-the-counter markets rather than established exchanges. This lack of regulation can lead to greater price volatility and the potential for significant losses. Additionally, companies associated with penny stocks might have a limited track record or be in financial distress, making them susceptible to dramatic fluctuations based on market sentiment or operational issues.

In comparison, domestic stocks, while they can also carry risk, are generally more stable due to their presence on major exchanges and better regulatory oversight. Social security income is not an investment and therefore involves no investment risk, but rather serves as a guaranteed source of retirement income. International bonds, while they may carry some degree of risk related to currency fluctuations and geopolitical factors, typically offer a level of stability that is not found in penny stocks. These attributes contribute to the categorization of penny stocks as a distinctly higher risk investment option.