The correct answer is D. Padmasambhava.
Padmasambhava, also known as Guru Rinpoche, was an Indian Buddhist master who is credited with introducing Buddhism to Tibet in the 8th century. He is considered to be the founder of Tibetan Buddhism and is revered by Tibetan Buddhists as the second Buddha.
Nagarjuna was an Indian Buddhist philosopher who lived in the 2nd century CE. He is considered to be one of the most important figures in the development of Mahayana Buddhism. He is best known for his work on the Madhyamaka philosophy, which emphasizes the emptiness of all phenomena.
Ananda was a close disciple of the Buddha. He is said to have memorized the Buddha’s teachings and is considered to be the author of the Pali Canon, the oldest collection of Buddhist scriptures.
Asanga was an Indian Buddhist philosopher who lived in the 4th century CE. He is considered to be one of the founders of the Yogacara school of Buddhism. He is best known for his work on the Yogacara philosophy, which emphasizes the mind and its role in understanding reality.
In conclusion, the Buddhist monk who spread Buddhism in Tibet was Padmasambhava.