Where does Excel's NOW function retrieve the date and time from?

Which of the following states the Rule of Entity Integrity?

a. Every row must have a value for the primary key and each value must be unique. b. Every foreign key must appear as another table’s primary key. c. Every row must have a value for the primary key and values may be repeated. d. None of the above.

________________ is data that is used to describe the content or structure of the actual data in a file.

Fill in the blank(s) with the appropriate word(s).