The University of California-Berkeley Extension, a unit of the university, offers dozens of online and classroom certificates among its 2,000 annual courses, in areas as diverse as accounting, paralegal studies and green chemistry, said Diana Wu, dean of the extension and executive director of the Berkeley Resource Center for Online Education, another university unit. “Students who need to develop a specific skill, brush up on a new or advanced industry best practices or fulfill a prerequisite for a graduate program can take one or two online courses or the entire certificate curriculum,” Dr. Wu said. The Berkeley Extension began offering online certificates about a decade ago, Dr