Answer : 4. "अभी तक सही पहचान नहीं हो पाई है"
Explanation :

The Indus script, also known as the Harappan script, is a pictographic script developed during the Indus Valley Civilization. The inscriptions on these symbols are very small. It is difficult to decide whether these symbols involved any writing system. Therefore experts are having difficulty in understanding the pictographic script.