SSC CGL 2021 Tier 1 Response sheet is available on the official website: ssc.nic.in
OR
you can access the link directly-
https://ssc.nic.in/ChallengeSystem/ChallengeHomescreen
Click on the above link, select the exam.
Enter your credentials and match your answers.
You can check the correct/incorrect attempts and can have an idea of your marks.
All the best guys!