Set X consists of the integers from 1 to 12, inclusive, while set Y consists of the integers from 0 to 20, inclusive. How many distinct integers do belong to the both sets at the same time?  Choose the correct choice from the following answers
A) 12	B) 15	C) 10	D) 20	E) 8

Rationale: x = { 1,2 , 3,4 , 5,6 , 7 , 8 , 9 , 10 , 11 , 12 } y = { 0 , 1,2 , 3,4 , 5,6 , 7 , 8 , 9 , 10 , 11,12 , 13,14 , 15,16 , 17,18 , 19,20 } common elements = { 1,2 , 3,4 , 5,6 , 7,8 , 9,10 , 11,12 } = 12 elements answer : option a .
Answer: A