The correct answer is option 2 - 1 and 2 only.

Let`s dissect each option to better understand the reasons for floods becoming a destructive hazard in the Ganga-Brahmaputra valley:

1. Due to population pressure more and more people are living in flood-prone areas: This statement is true. As population increases, more people tend to settle in areas that are prone to floods. This increases the risk and potential damage caused by floods.

2. Increased frequency and magnitude of landslides and soil erosion in the upper catchments: This statement is also true. Floods in the Ganga-Brahmaputra valley are often caused by heavy rainfall and the subsequent overflow of rivers. However, the increased frequency and magnitude of landslides and soil erosion in the upper catchments contribute to the volume of water that reaches the rivers, exacerbating the flooding.

3. Increase in the amount and intensity of rainfall in the north-western part of India: This statement is not directly related to the Ganga-Brahmaputra valley. While it is true that an increase in rainfall can contribute to flooding, the Ganga-Brahmaputra valley is primarily located in the northeastern part of India and is more affected by the monsoon rains from the Bay of