15. Which one of the following statements best defines the efficient market hypothesis? A. Efficient markets limit competition. B. Security prices in efficient markets remain steady as new information becomes available. C. Mispriced securities are common in efficient markets. D. All securities in an efficient market are zero net present value investments. E. Profits are removed as a market incentive when markets become efficient. 16.A news flash just appeared that caused about a dozen stocks to suddenly drop in value by about 20 percent. What type of risk does this news flash represent? A. portfolio B. nondiversifiable C. market D. unsystematic E. total