Which file should be edited to select the network locations from which Debian installation package files are loaded?

Which file should be edited to select the network locations from which Debian installation package files are loaded?

A.
/etc/dpkg/dpkg.cfg

B.
/etc/apt/apt.conf

C.
/etc/apt/apt.conf.d

D.
/etc/apt/sources.list

E.
/etc/dpkg/dselect.cfg