Explanation:

- The speed of the boat in still water is 12 km/h.

- Against the current, it takes three times as long to cover the same distance.

- Therefore, it takes 3 hours to travel 12 km against the current.

- Speed against the current = distance / time = 12 km / 3 hours = 4 km/h.

- Let the speed of the current be 'x' km/h.

- The effective speed of the boat against the current = speed in still water - speed of current.

- Hence, 12 - x = 4.

- Solving for x gives: x = 8 km/h.

- Option 1: 8 km/h