What does radioactive mean?

A. Absorbing high-energy electromagnetic radiation

B. Emitting radiation as a result of unstable nuclei

C. Having electron transitions at radio-wave frequencies

D. Generating positively or negatively charged ions

B. Emitting radiation as a result of unstable nuclei.

Explanation:

Radioactive by definition is "Radioactivity is the spontaneous emission of radiation in the form of particles or high energy photons resulting from a nuclear reaction". So we would assume that the answer would be B.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.