Multiple choice general knowledge science & technology Thermonuclear runaway is Uncontrolled fusion of hydrogen into helium Uncontrolled fusion of hydrogen into lithium controlled fission of hydrogen into helium controlled fission of hydrogen into lithium Reveal answer Fill a bubble to check yourself A Correct answer Explanation Thermonuclear runaway occurs when uncontrolled fusion reactions convert hydrogen into helium in stellar cores, releasing enormous energy. This process powers stars and can lead to supernovae.