The correct option is A gravity
∙ Gravity is a force of attraction. It is a force that each body exerts on the other to pull or attract it towards itself.
∙ The Earth exerts a force of gravitation on all objects that attracts everything towards the center of the Earth.
∙ If we throw something in the air, it falls back to the ground because of the Earth's gravity.
∙ It is because of this force that everything on Earth is so stable.