A swimmer can swim in still water at 4 km/h. If the speed of the water current is 2 km/h, how many hours will the swimmer take to swim against the current for 5 km?  Choose the correct choice from the following choices:  A) 2.0  B) 2.5  C) 3.0  D) 3.5  E) 4.0

Rationale: "the swimmer can swim against the current at a speed of 4 - 2 = 2 km / h . the time it will take is 5 / 2 = 2.5 hours . the answer is b ."
Answer: B