Final answer:
The novel by James Hilton that describes a hidden utopian paradise in Tibet is 'Lost Horizon'. So, the correct answer is option a.
Step-by-step explanation:
The 1933 novel written by James Hilton about a tired traveler who stumbles upon a peaceful, prosperous utopia hidden in the mountains of Tibet is Lost Horizon.
This novel introduced the mythical paradise of Shangri-La, a harmonious valley, guided by lamasery, where people live unusually long lives amidst an idyllic setting secluded from the outside world. The story follows the character Hugh Conway who, along with other passengers, is hijacked and taken to this peaceful land.