The headquarters of the Lower Assam division is located in:

The correct answer is: a) Dibrugarh.

Dibrugarh is a city in the Indian state of Assam. It is the headquarters of Dibrugarh district and the Upper Assam division. The city is located on the banks of the Brahmaputra River, about 450 kilometers east of Guwahati. Dibrugarh is a major commercial and educational center in Assam. It is also home to a number of industries, including tea, oil, and natural gas.

The other options are incorrect because:

• Guwahati is the capital of Assam and the headquarters of the Lower Assam division.
• Silchar is the headquarters of Cachar district and the Barak Valley division.
• Tezpur is the headquarters of Sonitpur district and the North Assam division.