Respond to the following comments by firstly judging whether they are right or not, and then give your reasons: 

a. The capital markets are similar to a casino if stock prices follow a random walk;

b. If markets are efficient, you could simply select your portfolio by throwing darts at the stock listings in The Financial Review;

c. Researchers have identified that CEOs and Board of directors in the firm could earn better returns compared to normal investors. This implies that the market is weak or semi-strong efficient;

d. Assume that a company announces an unexpected large cash dividend to its shareholders. In an efficient market without information leakage, one might expect an abnormal price change at the announcement.