In the Following Shorthand Representation of a Database, the Underlined

Multiple Choice

In the following shorthand representation of a database, the underlined items are _____.
INVOICES (INVOICE_NUM, INVOICE_DATE, CUST_ID)
INVOICE_LINE (INVOICE_NUM, ITEM_ID, QUANTITY, QUOTED_PRICE)
ITEM (ITEM_ID, DESCRIPTION, ON_HAND, CATEGORY, LOCATION, PRICE)

A) relations
B) entities
C) nonkey columns
D) primary keys