Planets take in _ and release oxygen gas

Carbon dioxide (CO₂)

Plants use a process called photosynthesis.  During this process, they take CO₂ from the air and water from their roots and combine them.  Then, using energy from sunlight, they convert these ingredients into carbohydrates and oxygen, and the extra oxygen is released into the atmosphere.

explanation:

the universal gravitation equation. since the gravitational force is directly proportional to the mass of both interacting objects, more massive objects will attract each other with a greater gravitational force. if the mass of one of the objects is doubled, then the force of gravity between them is doubled.