Passage: "The 'efficient market hypothesis' (EMH) posits that asset prices fully reflect all available information. This implies that it is impossible to consistently 'beat the market' through active trading, as any new information is immediately incorporated into prices. Critics of EMH often point to market anomalies, such as predictable patterns in stock returns or the existence of speculative bubbles, as evidence against its strong forms. They argue that investor psychology, information asymmetry, or structural market inefficiencies can prevent prices from always reflecting true underlying value. While EMH remains a cornerstone of financial theory, the debate over its practical implications for investors and policymakers continues." Which of the following, if true, would most directly challenge the 'strong form' of the efficient market hypothesis?

1. AA fund manager consistently earns higher returns than the market average by analyzing publicly available financial reports.
2. BThe stock market experiences a period of prolonged volatility due to geopolitical events.
3. CInsider trading, which uses non-public information, is found to be profitable for those who engage in it.
4. DAcademic studies show that market prices react quickly to major corporate announcements.