A boat's current flows at a speed of 4 km per hour. In it a boat goes 6 km and comes back to its starting point in 2 hours. Accordingly, what will be the speed of that boat in still water?

• A. 6 किमी/घंटा
• B. 8 किमी/घंटा
• C. 7.5 किमी/घंटा
• D. 6.8 किमी/घंटा