Can someone explain? Thanks!

Consider this simple greedy algorithm for making change that totals N cents while (N>0) take a coin of the largest denomination D N N D s N For which set of denominations below does the greedy algorithm always take the fewest number of coins to make change, for every positive integer value of N? a) (1,4,6,12) b) (14,8,10,12) c) (1,3,5,8,12) d) 1,3,5,10,15