You want to add user tux to the southpole group without changing his primary group membership. Which command do you use for this purpose?
A. useradd -g southpole tux
B. usermod -g southpole tux
C. groupadd -A tux southpole
D. groupmod -A tux southpole
in order to add them to a group without changing the primary group you would need to append.
usermod -aG southpole tux
The above do not satisfy the requirement. Also the group southpole would need to exist