Final answer:
The best description of scientists' interest in supernovas is that they provide insights into the life cycle of stars, contribute to the formation of elements necessary for life, and serve as tools for measuring cosmic distances.
Step-by-step explanation:
The quote that best describes why scientists are interested in supernovas is "Supernovas provide crucial insights into the life cycle of stars." This is because after a supernova explosion, the death of a massive star takes place which is a significant event in the history of its galaxy. The elements built up by fusion during the star's life are now "recycled" into space by the explosion. These elements enrich the gas and dust that form new stars and planets, crucial for the formation of planets and the origin of life. Additionally, supernovas are sources of high-energy cosmic ray particles which may influence the evolution of life on Earth. Type Ia supernovas, in particular, are used as "standard bulbs" for measuring distances to other galaxies due to their consistent luminosity.