Explanation:

- The boat's speed in still water is 6 km/h.

- The stream's speed is 2 km/h.

- Upstream speed = 6 - 2 = 4 km/h.

- Downstream speed = 6 + 2 = 8 km/h.

- Let the one-way distance to the place be 'd' km.

- Time taken to go upstream = d/4 hours.

- Time taken to come back downstream = d/8 hours.

- Total time for round trip = d/4 + d/8 = 6 hours.

Solve for 'd':

- Multiply entire equation by 8 to clear fraction: 2d + d = 48 ? 3d = 48 ? d = 16 km.

- Option 1: 16 km is correct.