Question

what is the particle that is labeled with a question mark (?) in the diagram? beta particle quark nucleus alpha particle

Explanation:

Quarks are elementary particles that make up protons and neutrons. Beta particles are high - energy electrons or positrons emitted during radioactive decay. Nucleus is a part of an atom (not a particle that makes up protons). Alpha particles are made up of two protons and two neutrons. Since protons and neutrons are made of quarks, the particle labeled with a question mark (which is part of protons) is a quark.

Answer:

quark