Detailed Instructions: This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
Problem:Passage: The history of a unified Tibet begins with the rule of Songtsän Gampo (604–650 CE), who united parts of the Yarlung River Valley and founded the Tibetan Empire. He also brought in many reforms, and Tibetan power spread rapidly, creating a large and powerful empire. It is traditionally considered that his first wife was the Princess of Nepal, Bhrikuti, and that she played a great role in the establishment of Buddhism in Tibet. In 640 he married Princess Wencheng, the niece of the powerful Chinese emperor Taizong of Tang China. Question: Who founded the Tibetan Empire?
Solution:
Songtsän Gampo