Tickets numbered from 1 to 21 are mixed and then a ticket is selected randomly. What is the probability that the selected ticket bears a number which is a multiple of 3?	Choose one.
A) 1 / 3
B) 2 / 5
C) 3 / 10
D) 3 / 7
E) 1 / 7

Rationale: "here , s = [ 1 , 2 , 3 , 4 , … . , 19 , 20 , 21 ] let e = event of getting a multiple of 3 = [ 3 , 6 , 9 , 12 , 15 , 18 , 21 ] p ( e ) = n ( e ) / n ( s ) = 7 / 21 = 1 / 3 the answer is a ."
Answer: A