214. In which decade was the telephone invented?

A. 1850s
B. 1860s
C. 1870s
D. 1880s
✅ The correct answer is option C.
Alexander Graham Bell’s notebook entry of 10 March 1876 describes his successful experiment with the telephone. Speaking through the instrument to his assistant, Thomas A. Watson, in the next room, Bell utters these famous first words, “Mr. Watson — come here — I want to see you”.

216. In which decade were the first successful diode and triode vacuum tubes invented?

A. 1800s
B. 1880s
C. 1890s
D. 1900s
✅ The correct answer is option D.
In 1904, John Ambrose Fleming invented the first practical electron tube called the ‘Fleming Valve’, which is a diode rectifier. In 1906, Lee de Forest invented the audion later called the triode, which provided signal amplification.

219. What is the World Wide Web?

A. A computer game
B. A software program
C. The part of the Internet that enables information-sharing via interconnected pages
D. Another name for the Internet
✅ The correct answer is option C.
The World Wide Web is a subset of the Internet. Specifically, the Web is a collection of documents and applications residing on Internet servers around the world.