To determine which two planets should be the closest in diameter on the scale model, we can look at the diameters provided:
- Mercury: 4,800 km
- Venus: 12,100 km
- Earth: 12,800 km
- Mars: 6,700 km
- Jupiter: 143,000 km
- Saturn: 120,000 km
- Uranus: 51,100 km
- Neptune: 50,000 km
Now, let's calculate the differences in diameter for each pair of planets to find the two that are closest in size:
- Earth (12,800 km) and Venus (12,100 km) have a difference of 700 km.
- Uranus (51,100 km) and Neptune (50,000 km) have a difference of 1,100 km.
- Mars (6,700 km) and Jupiter (143,000 km) have a huge difference of 136,300 km.
- Mercury (4,800 km) and Neptune (50,000 km) also have a huge difference of 45,200 km.
The smallest difference is between Earth and Venus (700 km), making them the closest in diameter.
Therefore, the correct response is:
Earth and Venus