The duplicate ratio of 2:6 is?
Choose one.
A) 1 : 2 B) 1 : 4 C) 1 : 9 D) 1 : 18 E) 1 : 13

Rationale: "2 ^ 2 : 6 ^ 2 = 4 : 36 = 1 : 9 answer : c"
Answer: C