Answer : 4. "10°N and 30°N"
Explanation :

1. The area of Ganga Brahmaputra basin is situated in 10°N to 30°N latitude.

2. The Ganga Brahmaputra Basin is located in the subtropical regions of the Indian subcontinent.

3. Ganga Brahmaputra Basin is a basin formed by the Ganges and Brahmaputra rivers and their tributaries.

4. Following are the characteristics of Ganga-Brahmaputra basin.

- This basin has rich plains, Himalayas and Sundarban delta.

- Area: 1,999,000 square kilometers

- Population: over 1.5 billion

- Main rivers: Ganga, Brahmaputra, Yamuna, Godavari, Mahanadi, and tributaries of Brahmaputra.

- Main crops: Paddy, wheat, maize, and pulses