Why Is the Ex-Dividend Date Important to Someone Who Is

Why is the ex-dividend date important to someone who is considering purchasing a firm's stock?

A) If the stock is purchased on this date or later the buyer will not receive the next dividend paid by the firm.
B) This is the date the firm "opens its books" to determine the names of the persons who will receive the next dividend that will be paid.
C) This is the date the board of directors announces the value of the next dividend payment, so the market price of the stock will increase at this point.
D) This is the date the dividend is paid that is, dividend checks are mailed to investors.
E) The ex-dividend date really isn't very important to potential investors; this date is more important to accountants who construct financial statements because it is the date the dividend becomes a legal liability of the firm.