Answer the following question given this paragraph: 

Reactivity is the ability of matter to combine chemically with other substances. For example, iron is highly reactive with oxygen. When it combines with oxygen, it forms the reddish powder called rust (see Figure below ). Rust is not iron but an entirely different substance that consists of both iron and oxygen.


Q: What term describes the ability of matter to combine chemically with other substances?

 Choices:

- oxidation

- Diffusion

- permeability

- reactivity

A:
reactivity
