Correct Option (A)
Inference 1 is correct. The passage explicitly states that the damage to tea plantations along the Brahmaputra floodplains, including loss in productivity, is due to the rising level of the river bottom from siltation and the changing course of the river system. It further attributes high erosion rates in major river systems like the Ganga and Brahmaputra to deforestation and ill-suited land management practices. Therefore, deforestation, by contributing to siltation, can lead to alterations in river courses.
Incorrect Options:
Inference 2 is incorrect. The passage mentions "salinization of land as in the semi-arid and arid 'green revolution' areas of the country," providing an example of human-induced salinization. However, it does not assert that human activities are the exclusive cause of salinization. Natural processes can also contribute to land salinization, and the passage does not negate this possibility.
Inference 3 is incorrect. The passage identifies "monotonous monoculture of rice/wheat across the Indian plains" as a factor contributing to "site quality decline," which is a form of ecosystem impoverishment. While this links monoculture to land degradation, the passage does not state that intense monoculture practice is a major reason for desertification specifically in Tropical Asia, Africa, and South America. For these regions, the passage primarily attributes increasing erosion rates to deforestation and ill-suited land management practices.