When Eric's grandfather migrated to the United States, he had completed six years of schooling and worked as a grape - picker in California. Eric' father completed high school and worked for twenty years as a clerk in a large state agency. Through the efforts of his father and grandfather, Eric was able to graduate from college and medical school, and he now has a thriving medical practice in southern California. Eric's family exemplifies _________ mobility.

A. intrágenerational
B. intergenerational
C. distributional
D. structural