Concept:Detection of phosphine gas in a planet’s atmosphere is linked to possible biological activity.Explanation:In September 2020, astronomers detected phosphine gas in the thick clouds of Venus.Phosphine on Earth is often produced by microbial life, which raised the possibility of life in Venus’s acidic clouds.This discovery made Venus a key focus in the search for signs of life.Among the given options, Venus is the correct planet.Answer:Option C: Venus