Final answer:
Terrestrial radiation is chiefly an example of b. natural background radiation. It originates from naturally occurring radioactive materials in the Earth's crust and atmosphere.
Step-by-step explanation:
Terrestrial radiation is primarily an example of natural background radiation. This is radiation that is constantly present in our environment and comes from natural sources such as the ground, air, and even our own bodies.
Terrestrial radiation originates from radioactive materials, like uranium and thorium, in the earth's crust and in the atmosphere. While terrestrial radiation does consist of alpha, beta, and gamma rays, the term itself is most directly synonymous with natural background radiation.
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