Question: 20th Century Boys was a heavy metal pairing of German lead vocalists Michael Bormann of Jaded Heart and Michael Voss of Mad Max, the duo recorded 11 songs by T. Rex as a tribute to Marc Bolan and released them as an album called "Beware of the Rex!", Bolan was an English singer-songwriter, musician, guitarist, and poet, best known as the lead singer of which glam rock band?
Answer: T. Rex