A practical way to work through this is to lay out the acquisition process for Scheduled Tribes land as a sequence of steps, and see which option correctly reflects the order and necessity of those steps.
Since only this last option correctly sequences and requires both safeguards as genuine preconditions, that is the accurate legal position, and the correct answer is that SIA and Gram Sabha consultation and consent are mandatory for ST land, with acquisition unable to proceed without consent.
Another way to reach the same result is to focus on the underlying purpose of these safeguards, protecting a vulnerable community's connection to its land, and test each option against whether it actually serves that purpose.
Since only making both the Social Impact Assessment and Gram Sabha consent mandatory actually protects Scheduled Tribes from involuntary displacement, that is the position the law takes, making it the correct answer.