Which of the following is a subset of z = {0, 20, 40, 60, 80, 100, 120}?
a. j = {20, 40, 110, 120}
b. k = {20, 40, 80, 100}
c. l = {0, 20, 70, 100}
d. m = {0, 20, 40, 110}'