Answer -- (b) X-Ray Machine
Sir Wilhelm Roentgen, was a German professor of physics. He was the first person to discover electromagnetic radiation in a wavelength range commonly known as X-rays today. Even though, many people had observed the effects of X-ray beams before, but Wilhelm Roentgen was the first one to study them systematically. To uncover the unknown nature of his discovery, they called him X-ray, though he is still known as Roentgen-rays. For his remarkable achievement, he was honored with the first he first Nobel Prize in Physics in 1901.
