apt-get update question

[Stephen Liu <satimis@icare.com.hk>]

Hi folks,

Following is the content of /etc/apt/sources.list in my Debian box

#deb copy:///cdrom/ sarge main

deb cdrom:[Debian GNU/Linux testing _Sarge_ - Official NetInst Snapshot i386 
Binary-1 (20031118)]/ unstable contrib main

deb ftp://ftp.debian.org/debian/ testing main
deb-src ftp://ftp.debian.org/debian/ testing main

deb http://security.debian.org/ stable/updates main contrib

deb ftp://ftp.debian.org/debian/ stable main  contrib
deb-src ftp://ftp.debian.org/debian/ stable main  contrib


If I expect update only taking effect on "testing main" whether I have to 
comment out;
# deb http://security.debian.org/ stable/updates main contrib
# deb ftp://ftp.debian.org/debian/ stable main  contrib
# deb-src ftp://ftp.debian.org/debian/ stable main  contrib

And if I expect update only taking effect on "stable main" whether I have to 
comment out;
# deb ftp://ftp.debian.org/debian/ testing main
# deb-src ftp://ftp.debian.org/debian/ testing main

I failed to find information on man apt-get

Kindly advise

TIA

B.R.
Stephen Liu