9. The post-eanings announcement drift (PEAD) refers to a phenomenon that stock prices show positive (negative) drifts for a few months after positive (negative) earnings announcements.If we frequently oa stock market, we would be able to reject a. only the weak-form efficient market hypothesis. b. only the semi-strong form efficient market hypothesis. c. both the semi-strong form and the strong-form efficient market hypotheses d. only the strong-form efficient market hypothesis. e. None of the above options is correct