A boat takes a total time of three hours to travel downstream from P and Q and upstream back from Q to P. What is the speed of the boat in still water? I. The speed of the river current is 1 km per hour. II. The distance between P and Q is 4 km.

1. A Option A: I alone sufficient while II alone not sufficient to answer
2. B Option B: II alone sufficient while I alone not sufficient to answer
3. C Option C: Either I or II alone sufficient to answer
4. D Option D: Both I and II are not sufficient to answer
5. E Option E: Both I and II are necessary to answer

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