Which sentence can represent the inequality n/4.2 < _ 21
a. the quotient of a number and 4.2 is less than or equal to 21.
b. the quotient of a number and 4.2 is less than 21.
c. the quotient of 4.2 and a number is less than or equal to 21.
d. the quotient of 4.2 and a number is less than 21.