Janiya is taking a road trip. The distance she plans to travel can be written as 3×102

To determine which distance uses the most appropriate units, we need to consider the typical scale of a road trip.

1. **3 × 10² kilometers** = 300 kilometers
2. **3 × 10⁵ meters** = 300,000 meters
3. **3 × 10⁷ centimeters** = 30,000,000 centimeters
4. **3 × 10⁸ millimeters** = 300,000,000 millimeters

Typically, road trip distances are measured in kilometers or miles, as they are more practical for longer distances.

Based on this, the most appropriate unit for a road trip distance is **3 × 10² kilometers** (300 kilometers).

Hence, the most appropriate choice is:

**3 × 10² kilometers (3 times 10 squared kilometers)**.