Yes, you can file RTI for Copy of your Answer Sheet from Assam Higher Secondary Education Council (AHSEC).
AHSEC was established by the Assam government on 01/06/1984 to regulate, supervise and develop the system of higher secondary education in the State of Assam. It is the regulating body for Higher Secondary (10+2 stage) education in the State of Assam. AHSEC is a "Public Authority" as per Section 2 (h) of the RTI Act 2005 and falls under its ambit.
You can file RTI to obtain Certified Copies of your Answer / OMR Sheets under Section 2 (j) of the RTI Act from AHSEC by addressing the same to the designated "Public Information Officer (PIO)" through Registered Post and by paying the prescribed fee. You should attach a Copy of your Admit Card and mention your Roll No., Registration No., Name of the Exam clearly in the Application.
To know more about the procedure to file RTI Application for Exam Paper, please refer https://onlinerti.com/how-to-file-rti-online-for-exam