In the following diagram, there are 3 intersecting circles intersecting showing 3 different classes, one showing those candidates who are educated in computers, second showing those who know rules and regulations of office and third showing graduates. Each part of the diagram is represented by a letter.Which letter represents those candidates who are educated in computers but are neither graduates nor know rules and regulations of office?

• A. a
• B. b
• C. c
• D. d