Answer : 3. "अलाउद्दीन खल्जी"
Explanation :

1. During the reign of Alauddin Khilji, Mongols attacked Delhi the most number of times.

2. First in the year 1299 and then in 1302-03. Alauddin Khilji built a new garrison town called Siri for his troops.

3. The administrative measures of Muhammad Tughlaq failed.