Which of the following statements regarding cash dividends is true?

$$ a$)$ Cash dividends to common and preferred stockholders are variable amounts.

b$)$ Cash dividends are guaranteed payments to preferred and common stockholders.

$$ C$)$ Growth and speculative companies typically pay little or no cash dividends.

$$ d$)$ All after$-$tax earnings of a corporation must be paid out in the form of dividends to the common and preferred stockholders.