Task: Question Answering
Input (English): Question: A boat crossed a lake from East to West at the speed of 5 km/h, entered a river and covered twice as much distance going upstream at 4 km/h. It then turned around and stopped at the south shore of the lake. If it averaged 3.6 km/h that day, what was its approximate downstream speed?

 Option A: 4

 Option B: 5

 Option C: 6

 Option D: 7

 Option E: 8
Output (English): Option C