Here's the citation

Go to download 485 instruction PDF file (revised 7/30/07) from USCIS (or google.com).
Go to Page 4, check under item 13. It says: You must sub-mit a completed Form G-325A if you are between 14 and 79 years of age.

See also other non-official sources:


http://www.umsl.edu/~intelstu/scholars/documents/adjustmentinstructions.pdf

http://au.answers.yahoo.com/answers2/frontend.php/question?qid=20071206203159AATY9Jq

Thanks for greetings! Merry Xmas to your family too.