Answer:
B. Only attorneys.
Step-by-step explanation:
A Professional organization is where professionals of the same kind gather to oversight or control the correct practice of the occupation. In this case, an attorney's organization will foresee the correct appliance of the law and the avoidance of false attorneys that looks to fraud the citizens.
To be part of the organization the members need to be part of what the organization represents, a medic can not be part of an attorney's organization for example.
I hope this answer helps you.