Land acquisition law lays down a clear order of steps precisely so that people likely to be displaced, especially tribal communities, get a real say before their land is taken. Preliminary notification comes first, followed by a Social Impact Assessment, then consultation with and consent of the Gram Sabha where tribal land is involved, and only then a final notification.
Once the correct sequence and the special protection for tribal land are kept in view, the statement that both the assessment and the Gram Sabha's consent are mandatory, and that acquisition cannot proceed without that consent, stands out as accurate.
So, the correct answer is SIA and Gram Sabha consultation/consent are mandatory for ST land; acquisition can't proceed without consent.
Land acquisition legislation gives Scheduled Tribes land a higher degree of procedural protection than ordinary land, on the reasoning that tribal communities depend heavily on land and forest resources and are especially vulnerable to displacement.
The higher protection given to Scheduled Tribes land under the statute is best reflected in the option that treats both the assessment and the Gram Sabha's consent as mandatory, with no acquisition possible absent that consent.
Hence, the correct answer is SIA and Gram Sabha consultation/consent are mandatory for ST land; acquisition can't proceed without consent.