I, III, IV 正確 The subprime crisis case highlights the following lessons:(1)Credit ratings for different types of obligation should be clearly distinguished, and investors should not solely rely on ratings to make their investment decisions;(2)Appropriate policy should strike a balance between improving consumer protection and maintaining the viability of the securitization model;(3)Policymakers should resist pressure for bailouts in order to reduce the danger of reinforcing speculative or fraudulent behaviour.