If a: b = 3:4, b:c = 7:9, c:d = 5:7, find a:d? Choose the correct choice from the following options.
A) 5 / 12 B) 5 / 15 C) 5 / 10 D) 5 / 11 E) 5 / 13

Rationale: "a / d = ( 3 / 4 ) * ( 7 / 9 ) * ( 5 / 7 ) = > 5 / 12 answer : a"
Answer: A