________ is free software that is distributed with few licensing and copyright restrictions

The ________ keyword removes duplicates from query results

A) UNION B) AS C) DISTINCT D) ON

In what type of digital signal does the signal level move to one of the discrete signal levels, but returns to the zero level after a predetermined time?

a. Non-return-to-zero (NRZ) level. b. NRZ mark. c. NRZ space. d. Return-to-zero.