Answer the following question given this paragraph: 

For many decades, scientists have known that atoms consist of electrons and other particles called protons and neutrons. Recently they found that there are even smaller particles in atoms. Scientists call these extremely tiny particles by the funny name of quarks. As you can see in this diagram, there are several different kinds of quarks, called up quarks, down quarks, top quarks, bottom quarks, charm quarks, and strange quarks. In this chapter you’ll learn about these unusual particles and also other particles inside the atom.


Q: For many decades, scientists have known that atoms consist of electrons and other particles called protons and?

 Choices:

- rods

- waves

- nanoparticles

- neutrons

A:
neutrons
