As You and a Friend Are Entering a Chemistry Laboratory

As you and a friend are entering a chemistry laboratory at your university,you see a sign that states in big,bold,red letters: DANGER-RADIOACTIVE ISOTOPES IN USE.Your friend is an accounting major and has not had any science courses yet.She asks you what a radioactive isotope is and you respond correctly using which of the following choices.

A) Radioactive isotopes are atoms that are unstable and as a result emit energy in a process called radioactive decay.
B) Radioactive isotopes are atoms that are stable and as a result emit energy in a process called radioactive decay.
C) Radioactive isotopes are atoms that are stable and as a result only emit energy if they are exposed to higher temperatures.
D) Radioactive isotopes are atoms that are unstable but unless actively disturbed by some chemical process will remain intact and pose no problems.