Radioactivity is
A. the spontaneous emission of radiation from unstable elements.
B. the emission of light from certain substances after exposure to sunlight.
C. the spontaneous emission of radio waves from matter.
D. the emission of light from matter when exposed to radio waves.
Answer:A
Radioactivity is
A. the spontaneous emission of radiation from unstable elements. B. the emission of light from certain substances after exposure to sunlight. C. the spontaneous emission of radio waves from matter. D. the emission of light from matter when exposed to radio waves.