Here's the answer. Also my paper didn't have remarks so I have to do 3B and submit supporting documents.
Question 3A
Write your last name (surname/family name) and given name(s) exactly as they appear on your immigration document. If your name was shortened (truncated), write the name that appears in the “Remarks” section of your immigration document. The name in the “Remarks” section will have precedence over the name in the surname/family name section. Immigration documents include your:
Record of landing (IMM 1000)
Confirmation of Permanent Residence (IMM 5292 or IMM 5688)
Permanent resident card (PR card)
Question 3B
Write the last name (surname/family name) and given name(s) that you request to appear on your citizenship certificate and indicate the reason for the request.
If your name was shortened (truncated) on your immigration document and does not appear in the “Remarks” section of your immigration document you must provide one of the following supporting documents showing your full name:
Passport of entry displaying your full name (the passport you used to immigrate to Canada); or
Canadian visa counterfoil, or
Birth certificate issued prior to your date of entry to Canada (date you immigrated to Canada).
Have you legally changed your name or are you requesting a different name on your citizenship certificate than the name on your immigration document due to a minor or significant change in spelling?
If yes:
see Name change section in this guide in “Step 1. Gather Documents”
Note: A request for a different name is subject to approval by CIC.