Which of the following random variables is geometric?
(a) The number of phone calls revived in a one-hour period
(b) The number of cards I need to deal from a deck of 52 cards that has been thoroughly shuffled so that at least one of the cards is a heart.
(c) The number of digits I will read beginning at a randomly selected starting point in a table of random digits until i find a 7.
(d) The number of 7s in a row of 40 random digits.
(e) All of the above.