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19. Which of the following observations appear to indicate semi-strong market inefficiency? a. Managers make superior returns on their purchases of their company's stock. b. There is a positive correlation between the return on a broad market index in one quarter and the change in aggregate profits in the following quarter. c. Stocks of companies with unexpectedly high earnings appear to offer high returns for several months after the earnings announcement. A. a and b only B. a, b and c. C. c only D. a and c only E. b and c only