A person can swim in still water at 12 km/h. If the speed of water 10 km/h, how many hours will the man take to swim back against the current for 12km? Choose the correct choice.
A) 3  B) 4  C) 5  D) 6  E) 7

Rationale: "m = 12 s = 10 us = 12 - 10 = 2 d = 12 t = 12 / 2 = 6 answer : d"
Answer: D