Which one of the following statements best expresses the main idea of the passage? A. Tollefson's focus on the economic and cultural factors involved in adjusting to a new country offers a significant departure from most studies of Southeast Asian immigration. B. In his analysis of educational programs for Southeast Asian immigrants, Tollefson fails to acknowledge many of the positive effects the programs have had on immigrants' lives. C. Tollefson convincingly blames the philosophy underlying immigrant educational programs for some of the adjustment problems afflicting Southeast Asian immigrants. D. Tollefson's most significant contribution is his analysis of how Southeast Asian immigrants overcome the obstacles they encounter in immigrant educational programs. E. Tollefson traces a gradual yet significant change in the attitudes held by processing center educators toward Southeast Asian immigrants.