Did you appear for GATE 2018? The Indian Institute of Technology Guwahati (IITG) invites candidates to challenge GATE Answer Keys however you will need to pay for reevaluation. The GATE 2018 Challenge window shall remain open from 21 Feb to 23 Feb. For more go here
http://gate.iitg.ac.in/
http://gate.iitg.ac.in/