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 7 km? Select.
A) 3.0 B) 3.25 C) 3.5 D) 3.75 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 7 / 2 = 3.5 hours . the answer is c ."
Answer: C