Which of the following statements about the philosopher Shankara is/are true? 1. Shankara espoused a form of Vedanta called Advaita. 2. He elaborated on the philosophy of Gaudapada. 3. Shankara tried to demonstrate that the Upanishads and Brahmasutras contain a unified, systematic philosophy. 4. Shankara founded the Amanaya Mathas. Select the correct answer using the code given below.

Shankara (Adi Shankaracharya) is the foremost proponent of Advaita Vedanta. He built upon the philosophical foundation laid by his Paramaguru (Guru's Guru), Gaudapada. A major part of his work involved writing extensive commentaries on the principal Upanishads, the Brahmasutras, and the Bhagavad Gita (collectively known as the Prasthanatrayi) to demonstrate their underlying unity and consistency with the Advaita philosophy. The establishment of the four cardinal Mathas (monastic centres) in Sringeri, Dwaraka, Puri, and Badrinath is traditionally attributed to Shankara, aiming to consolidate the Advaita tradition across India, and these are often referred to as Amanaya Mathas.