The ratio between the sale price and the cost price of an article is 9:7. What is the ratio between the profit and the cost price of that article?  Choose the correct option:
A) 2 : 9  B) 2 : 7  C) 3 : 6  D) 2 : 0  E) 2 : 1

Rationale: "let c . p . = rs . 7 x and s . p . = rs . 9 x . then , gain = rs . 2 x required ratio = 2 x : 7 x = 2 : 7 answer : b"
Answer: B