Answer:
4. Rights theorists
Explanation:
Right theorists believe that there are some things which an individual should not do against other individuals because they hold some sort of moral rights.
The right theorists can either be realist or constructivist.
In the view of realists, the rights of the right holders is considered to be their intrinsic feature and one should recognize and respect those rights.
According to the constructivists, there is not any intrinsic feature of rights for the right holders. Individuals chose to grant the rights to others.
As in the questions, the observers are thinking about the welfare of the workers, they seem to be realist right theorists and believe that everyone have right to be safe.