CORRECT TEXT
Make user1, user2 and user3 belongs to training group.

Answer:

Explanation:
1. usermod -G training user1
2. usermod -G training user2
3. usermod -G training user3
4. Verify from : cat /etc/group
There are two types of group, I) primary group II) Secondary or supplementary group.
5. Primary Group: Primary group defines the files/directories and process owner group there can
be only one primary group of one user.
6. Secondary Group is used for permission. Where permission are defined for group members,
user can access by belonging to that group.
Here user1, user2 and user3 belong as supplementary to training group. So these users get the
permission of group member.