I can only see the section C that will be applicable to you and your Parents. Because it is pertaining to Residents and those who will be landing to become residents. hence the choice is only that.

Since your Parents are the SENIOR most out of the lot, they will be filling in the form for the landing, if you all four are traveling together on the same flight. If not, you fill in your card and they do theirs on the last leg of their flight. But they will only have the date for LANDING. None in the column for date left. All of this is true, if only four people are traveling from the same family. If more than FOUR, then, you can use more than ONE form to complete the declarations for their landing.

AND, for the use of the CBSA they have their own way of identifying the traveler right on the top of the form and they do the needful to identify those who are Landing for the First time. They take care of he same. But the form is the same for one and all.

Hope this helps.

FH.
Pl.Attach the list of such goods that they will be bringing in plus the funds that they will be carrying in person.