What is the function of the Tab key on the Cisco Nexus Operating System command-line interface?

What is the function of the Tab key on the Cisco Nexus Operating System command-line interface?
A. redisplays the current command line
B. deletes all characters from the cursor to the end of the command line
C. clears the terminal screen
D. completes a partially entered command if enough characters are present
E. moves the cursor one word to the right