A man goes downstream at 13 kmph, and upstream8 kmph. The speed of the stream is  Choose the most appropriate option:  A) 0 kmph  B) 4 kmph  C) 16 kmph  D) 2.5 kmph  E) 26 kmph

Rationale: "speed of the stream = 1 / 2 ( 13 - 8 ) kmph = 2.5 kmph . correct option : d"
Answer: D