Based on the given characteristics of Planet A and Planet B, let's carefully identify each planet step by step.
### Analysis of Planet A:
1. Atmosphere is mostly carbon dioxide: This characteristic is very indicative of Mars. Mars is well-known for having a thin atmosphere composed primarily of carbon dioxide.
2. Surface is red: This characteristic further supports our hypothesis that Planet A is Mars, commonly known as the "Red Planet" due to its reddish appearance caused by iron oxide (rust) on its surface.
3. It has a few clouds: Mars has a much thinner atmosphere compared to Earth, and while clouds do exist, they are sparse and not as prevalent as on Earth.
### Conclusion for Planet A:
Given the above characteristics, Planet A is very likely Mars.
### Analysis of Planet B:
1. Atmosphere is rich in oxygen: This is a defining feature of Earth's atmosphere, which is composed of approximately 21% oxygen.
2. Surface has liquid water: Earth is the only known planet where liquid water exists abundantly on the surface in the form of oceans, rivers, and lakes.
3. It has many clouds: Earth’s atmosphere supports substantial cloud formation, which plays a crucial role in the water cycle and weather patterns.
### Conclusion for Planet B:
Given these characteristics, Planet B is certainly Earth.
### Final Identification:
Therefore,
- The identity of Planet A is Mars.
- The identity of Planet B is Earth.
