Option 1 states that the Chambal valley is marked by bad land topography. Bad land topography refers to the presence of eroded, steep slopes and ravines. While this may indicate the presence of a river or water flow, it is not specific to a rift valley. Therefore, option 1 does not provide the best evidence that a river is flowing through a rift valley.

Option 2 states that the River Tapi does not have a delta but only an estuary. A delta is a landform created by the accumulation of sediment at the mouth of a river, while an estuary is a partially enclosed coastal body of water where freshwater and saltwater mix. This statement suggests that the River Tapi flows through a rift valley because rift valleys often have steep walls that prevent sediments from accumulating and forming a delta. Therefore, option 2 provides the best evidence that a river is flowing through a rift valley.

Option 3 states that the River Mahanadi flows through a gorge at Satkosia. While gorges can indicate the presence of a river, they are not specific to rift valleys. Therefore, option 3 does not provide the best evidence that a river is flowing through a rift valley.

Option 4 states that the River Colorado has the