Final answer:
The intervention strategy most frequently used according to Spergel and colleagues cannot be determined without the specific study reference; however, in the context of McCarthy and Zald's resource mobilization theory, 'mobilization' would be a strategic focus.
Step-by-step explanation:
Based on the given information and the context of the research cited, it can be difficult to determine precisely which intervention strategy Spergel and colleagues found to be most frequently used without the proper study or document reference. However, in the concept of resource mobilization theory posited by McCarthy and Zald (1977), the key components involve the acquisition of resources and the mobilization of individuals to achieve the aims of a social movement. Thus, it would seem that 'mobilization' may be a fitting answer in the context of social movement success if the question concerns this theory. Nevertheless, without specific reference to Spergel and colleagues' study or findings, this answer cannot be confirmed with certainty. The claim about barriers to success, mentioning untreated trauma and family dysfunction, does not clearly indicate which intervention strategy was most used, but it highlights potential areas where interventions may focus.