Task: Question Generation
Input (English): Passage: An evil genius of unknown identity, calling himself "Dr. Vulcan" (heard only as a voice and seen as a mysterious shadow on a brightly lit wall), plots to conquer the world. He needs to first eliminate, one by one, the members of the Science Associates, an organization of America's greatest scientists. 
After narrowly escaping an attempt on his life by Vulcan, one member of Science Associates, Dr. Millard goes into hiding. He soon outfits another member, Jeff King with an advanced, atomic-powered rocket backpack, attached to leather jacket with a bullet-shaped, aerodynamic flight helmet, and a raygun that they had been developing together.
Using the flying jacket and helmet and other inventions provided by Dr. Millard, and aided by magazine reporter and photographer Glenda Thomas, Jeff King, as Rocket Man, battles Vulcan and his henchmen through a dozen action-packed Republic serial chapters. Eventually, Vulcan steals Millard's most dangerous invention, a Sonic Decimator, and uses it to flood, then destroy both New York City and the rest of Manhattan Island. The mysterious Dr. Vulcan is eventually unmasked and brought to justice by Jeff King while in his Rocket Man persona.
Output (English): What is used to hide Jeff Kings identity?