IIT Guwahati has released GATE 2018 response sheets of candidates.IIT Guwahati will publish officila answer key also in next few days.

Meawhile you can check various coaching institute answer key below:
GATE Answer Key
Also, Use GATE College Predicotr to check your chances in IIT, NIT and PSUs.
GATE College Predictor

Hello Megha,

Check the below link address where you will get the answer key for gate exam in civil engineering

https://exams.collegedunia.com/news/e-60-gate-2018-civil-engineering-ce-answer-key-question-paper--analysis

Regards