- Gravity causes objects that have mass / substances to be pulled down / to fall on a planet
- Marble is a kind of object / material
- Gravity is a kind of force
- Therefore, gravity is the force that causes the marble to be pulled down on a planet

Therefore, gravity is the force that causes the marble to be pulled down on a planet
Q: A marble is dropped in a glass of water. Which force pulls the marble to the bottom of the glass?
Context:
- Gravity causes objects that have mass / substances to be pulled down / to fall on a planet 
- Marble is a kind of object / material 
- Gravity is a kind of force