Let D be a recurring decimal of the
form D = 0.a1a2a1a2a1a2a1a2,..., where digits a1 and a2, lie between 0 and 9.
Further, at most one of them is zero. Which of the following numbers
necessarily produces an integer, when multiplied by D?
a. 18
b. 108
c. 198
d. 288