The Fallout from a Nuclear Explosion and the Waste from a Nuclear

The fallout from a nuclear explosion and the waste from a nuclear reactor contain radioactive isotopes. The atoms of these isotopes

A) have unstable nuclei but are chemically indistinguishable from stable atoms.
B) have unstable nuclei and are chemically unstable.
C) are chemically unstable but their nuclei are indistinguishable from stable atoms.
D) emit a steady stream of X-ray radiation.