Answer: an absolutely personal and independent activity
Step-by-step explanation:
Since Schweitzer realized that direct human service can only be accomplished when one collaborates with an official organization, this shows that he wanted to be an absolutely personal and independent activity.
In such case, he wants an activity that will be free from the outside control. Other options are wrong as he wasn't really interested in funding of organizations, or increasing the number of official organizations that are dedicated to direct human service.