We must see what is the structure of matter in its smallest form. Matter is made up of atoms, and these in turn have smaller particles. Neutrons, protons and electrons.
Neutrons have no charge, so we can start to rule out this option.
Protons are positively charged and, like neutrons, are in the center of the atom. The number of protons is always the same and it is the number of these that gives an element its name.
The quarks, are so far the smallest particles in the universe, and are inside the neutrons and protons.
Now, the electrons revolve around the nucleus and are easier to withdraw, move away or approach the center of the atom. So when there is an induced charge, the electrons will be affected.
So, the answer will be: Electrons