Which of the Following Statements Is True

Which of the following statements is true?

A) On average, an announcement by a firm's board of directors that they will continue with their current dividend policy has no effect on the price of the stock.
B) Only the announcement that a firm will begin paying dividends for the first time has any effect on a stock's price.
C) On average, an announcement of an increase in dividend yields of 10 or more basis points results in a relatively large price increase.
D) Both A and C are true statements.