Final answer:
G. C. Oosthuizen's work on African Independent Churches relied on informants to gather information about these churches.
Step-by-step explanation:
G. C. Oosthuizen's work on African Independent Churches was focused on studying and documenting these churches. Oosthuizen's style of research relied heavily on informants, which are individuals who provide information and insights about a particular subject. In the context of African Independent Churches, informants would have been members or leaders of these churches who were willing to share their knowledge and experiences with Oosthuizen. By relying on informants, Oosthuizen was able to gather first-hand accounts and detailed information about the practices, beliefs, and history of these churches.