City X has a population 5 times as great as the population of City Y, which has a population twice as great as the population of City Z. What is the ratio of the population of City X to the population of City Z?	Choose the correct choice from the following answers
A) 1 : 8	B) 1 : 4	C) 2 : 1	D) 4 : 1	E) 10 : 1

Rationale: "x = 5 y , y = 2 * z x : y , y : z 5 : 1 , 2 : 1 10 : 2 , 2 : 1 so , x : z = 10 : 1 ( e )"
Answer: E