The correct option is 1, 2, and 3 because all three basins—Cambay, Cauvery, and Krishna-Godavari—have been identified as regions in India that contain significant shale gas resources. Shale gas, a type of unconventional natural gas, is trapped within fine-grained sedimentary rocks (shale) and is extracted using advanced technologies like horizontal drilling and hydraulic fracturing. Understanding the geographical distribution of these resources is crucial for energy security and policy formulation in India, particularly as the country seeks to reduce its dependence on fossil fuel imports and transition to more sustainable energy sources, a key theme relevant to the UPSC syllabus on energy resources and environmental management.