The correct answer is option 3, Venus. Venus is the hottest planet in the Solar System because of its dense atmosphere and greenhouse effect. The atmosphere of Venus is mostly composed of carbon dioxide, which traps heat and causes a runaway greenhouse effect. This leads to extreme temperatures on the planet`s surface, with an average temperature of about 900 degrees Fahrenheit (475 degrees Celsius). Venus`s atmosphere is so thick that it retains heat and creates a strong greenhouse effect, making it the hottest planet in the Solar System.

Option 1, Jupiter, is the largest planet in the Solar System but not the hottest. Option 2, Saturn, is known for its beautiful rings but is not the hottest. Option 4, Uranus, is an ice giant and doesn`t have the extreme temperatures like Venus.