Correct Answer: Tritium

Solution : The correct option is Tritium.

Tritium is a radioisotope of hydrogen, containing two neutrons in addition to a proton in its nucleus. It is symbolized as ³ H or T and is radioactive, emitting beta particles. Tritium is used in various applications, including nuclear fusion research, luminous paints, and hydrogen bombs. Its radioactivity makes it valuable in radiometric dating and biological research, albeit with safety precautions due to its potential hazards.