उपनिषदों में मुख्य रूप से प्रतिपादित दर्शन को किस नाम से जाना जाता है?

Who among the following was the guru (teacher) of Adi Shankaracharya?

Which of the six orthodox schools of Hindu philosophy closely resembles Jain philosophy in its dualistic view of soul and matter?

The Charvaka school of philosophy is also known as: