The ratio between the present ages of A and B is 7:3 respectively. The ratio between A's age 4 years ago and B's age 4 years hence is 1:1. What is the ratio between A's age 4 years hence and B's age 4 years ago? Choose the correct option:	A) 3 : 4	B) 3 : 0	C) 9 : 1	D) 9 : 2	E) 3 : 9

Rationale: "let the present ages of a and b be 7 x and 3 x years respectively . then , ( 7 x - 4 ) / ( 3 x + 4 ) = 1 / 1 4 x = 8 = > x = 2 required ratio = ( 5 x + 4 ) : ( 3 x - 4 ) = 18 : 2 = 9 : 1 . answer : c"
Answer: C