Answer the following question given this paragraph: 

Collision theory states that chemical reactions occur when atoms, ions, or molecules collide. In other words, these species need to make contact with one another in order for a reaction to take place. Based on this concept, along with a couple of other key points, collision theory helps to explain why certain factors will influence the rate of a chemical reaction.


Q: What states that chemical reactions occur when atoms, ions, or molecules collide?

 Choices:

- disturbance theory

- reaction theory

- elemental theory

- collision theory

A:
collision theory
