With regard to the assertion and reason, choose the correct option.
Assertion [A]: α, β and γ rays are emitted by disintegration of atomic nuclei of radioactive elements.
Reason [R]: Nuclear fallout contains radioactive elements.
An element subject to spontaneous degeneration of its nucleus accompanied by the emission of alpha particles, beta particlesor gamma rays is called a radioactive element. Nuclear fallout refers to the radioactive particles that fall on to the earth as a result of a nuclear explosion. Fallout particles vary in size from thousandths of a millimeter to several millimeters. Much of this material falls directly back down close to ground where the explosion happened within several minutes after the explosion, but some get dispered by winds over long distances. The fallout usually gets suspended in the atmosphere, 6 to 7 km above the earth's surface. These radionuclides also often settle down by rain and get mixed with soil and water. From there, they can easily enter the food chain and finally get deposited in the human body where they cause serious health hazards.