__________ are not emitted by radioactive substances.

ANS:C - protons

Protons are not emitted by radioactive substances. Alpha (α) particles, beta (β) particles, and positrons are all types of radiation emitted by radioactive substances as a result of nuclear decay processes. However, protons are not typically emitted by radioactive decay. Instead, they are stable particles found in the nuclei of atoms. To clarify:

• Alpha (α) particles are helium-4 nuclei consisting of two protons and two neutrons.
• Beta (β) particles are either electrons (β-) or positrons (β+), which are emitted from the nucleus during beta decay processes.
• Protons are stable subatomic particles found in the nucleus of atoms, each with a positive charge.
• Positrons are positively charged particles, equivalent in mass to electrons, and are emitted during certain types of radioactive decay processes, such as beta-plus decay.