Why is Venus the hottest planet?

Answer: Thick CO₂ atmosphere traps heat

Thick CO₂ atmosphere traps heat ✓ — Correct! Venus has a runaway greenhouse effect. Its atmosphere is 96% carbon dioxide and 90 times thicker than Earth's - like being 900 meters underwater! Sunlight passes through but heat can't escape. This trapped heat raises surface temperature to 464°C (867°F) - hot enough to melt lead. The thick clouds of sulfuric acid reflect sunlight but also trap heat. Even though Mercury is closer to the Sun, Venus is hotter because of this extreme atmospheric insulation.

Volcanoes heat the surface — Wrong. While Venus may have some volcanic activity, active volcanoes don't significantly contribute to its extreme surface temperature. The heat comes from solar energy trapped by the thick CO₂ atmosphere (greenhouse effect), not from internal volcanic heat.

Its core is extremely hot — Wrong. All planets have hot cores, but core heat doesn't significantly warm the surface. Venus's extreme 464°C surface temperature is caused by its thick CO₂ atmosphere trapping solar heat (greenhouse effect), not by heat from its interior rising to the surface.