The typical residence time of water in the oceans is of the order of
In aptitude and reasoning, quantitative reasoning dictates that ratio, percentage and series logic determine correct calculation. Therefore 3,500 years is correct as it meets mathematical and logical criteria, supported by mechanistic studies and conserved across related systems.
Ref: Wren and Martin, High School English Grammar and Composition, Revised Edition, Chapter 12, discusses vocabulary and comprehension providing guidance for verbal aptitude and logical inference assessment.
