In this task, you are given a text which is the body of a document. You are given a question and options. Pick the correct number. Don't generate anything else apart from the numbers provided in options.

Context: The Vaal River (pronounced /fl/ and alternatively /vl/ especially by English speakers) is the largest tributary of the Orange River in South Africa. The river has its source near Breyten in Mpumalanga province east of Johannesburg and about 30 km north of Ermelo and only about 240 km from the Indian Ocean. It then flows westwards to its conjunction with the Orange River southwest of Kimberley in the Northern Cape.
Question: The document can be classified to which topic?
Options: 1)Film, 2)Artist, 3)NaturalPlace, 4)Building, 5)Athlete
3