For which discovery did William Bradford Shockley, John Bardeen and Walter Houser Brattain jointly receive the Nobel Prize in Physics in 1956?

Correct option is A

The correct answer is (a) Discovery of transistor effect.
 William Bradford Shockley, John Bardeen, and Walter Houser Brattain jointly received the Nobel Prize in Physics in 1956 for their groundbreaking work on semiconductors and the discovery of the transistor effect.
 This invention revolutionized electronics and laid the foundation for modern computers and other digital devices.
 Discovery of thermionic emission: This phenomenon was discovered in 1903 by Owen Richardson.
 Discovery of electromagnetic induction: This fundamental principle of electromagnetism was discovered by Michael Faraday in 1831.