Correct Option: C

In electronics, a vacuum tube, thermionic valve, tube, or valve is a device controlling electric current through a vacuum in a sealed container. The container is often thin transparent glass in a roughly cylindrical shape. Sir John Ambrose Fleming (29 November 1849 – 18 April 1945) was an English electrical engineer and physicist. He is known for inventing the first thermionic valve or vacuum tube, the diode, then called the kenotron in 1904. He is also famous for the left hand rule (for electric motors).