Based on Figure (a), which of the following statement is TRUE? STAFF staff_ID {pk} staff_name phone email { optional, or } HR SALES R&D HR_focus commission_rate product_focus research_exp...

Extracted text: Based on Figure (a), which of the following statement is TRUE? STAFF staff_ID {pk} staff_name phone email { optional, or } HR SALES R&D HR_focus commission_rate product_focus research_exp research_area Figure (a) O A. R&D staffs will not have the basic information (i.e.: id, name, phone, and email) B. A HR staff cannot be a Sales staff or R&D staff at the same time. O C. A staff can be a HR staff and Sales staff at the same time. O D. All the staffs are categorized into three subclasses.