Q: In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.
Question: Which is the oldest valley that Upper Paleolithic tools were found in? Passage:Although there is no evidence of lower or middle Paleolithic settlements in Tripura, Upper Paleolithic tools made of fossil wood have been found in the Haora and Khowai valleys. The Indian epic, the Mahabharata; ancient religious texts, the Puranas; and the Edicts of Ashoka – stone pillar inscriptions of the emperor Ashoka dating from the third century BCE – all mention Tripura. An ancient name of Tripura is Kirat Desh (English: "The land of Kirat"), probably referring to the Kirata Kingdoms or the more generic term Kirata. However, it is unclear whether the extent of modern Tripura is coterminous with Kirat Desh. The region was under the rule of the Twipra Kingdom for centuries, although when this dates from is not documented. The Rajmala, a chronicle of Tripuri kings which was first written in the 15th century, provides a list of 179 kings, from antiquity up to Krishna Kishore Manikya (1830–1850), but the reliability of the Rajmala has been doubted.
 Links: a. Puranas b. Haora River c. Upper Paleolithic d. Haora River
A:
b