Final answer:
The correct option is 'a) Warmer; atmosphere traps heat.' Earth's atmosphere traps heat from the Sun, preventing it from escaping back into space and keeping the planet warmer.
Step-by-step explanation:
The correct option is a) Warmer; atmosphere traps heat. Earth's atmosphere plays a crucial role in regulating the planet's temperature. The atmosphere contains greenhouse gases like water vapor and carbon dioxide, which trap heat from the Sun and prevent it from escaping back into space. Without this greenhouse effect, Earth would be much colder, and the oceans would be permanently frozen.
Other planets in our solar system, like Mars and Venus, have different atmospheres that result in extreme temperatures. Mars has a very thin atmosphere and little greenhouse warming, making it much colder than Earth. Venus, on the other hand, has a thick atmosphere of carbon dioxide, leading to intense greenhouse warming and extremely high temperatures.