Explanation:

The correct answer is Option 2: Hathnora. Let me explain further:

- Pachmarhi: This is a hill station in Madhya Pradesh, India, known for its natural beauty and tourist attractions. It is not recognized for any major prehistoric human fossil discoveries.

- Hathnora: This site is part of the Narmada Valley in Madhya Pradesh. It is famous for the discovery of a skullcap believed to belong to 'Homo erectus' or early archaic humans. This find is significant in studying the early presence of hominins in the Indian subcontinent.

- Patne: Located in Maharashtra, Patne is known for its archaeological importance but not for Homo erectus skull discoveries.

- Sanganakallu: This prehistoric site in Karnataka is noted for its Neolithic settlements and ancient artifacts, not directly linked to Homo erectus fossils.

Hathnora holds a key place in the pre-historic landscape due to its association with early human remains.