Barney Learns That the Phone Number for His Friend Lacey

Multiple Choice

Barney learns that the phone number for his friend Lacey in his ADDRESS_BOOK table has been disconnected; thus, her number is now unknown to him. Which SQL statement should Barney use to update the table so as to reflect this unknown value?

A) SELECT PHONE_NO FROM ADDRESS_BOOK WHERE (NAME = 'Lacey') SET NULL;
B) ALTER ADDRESS_BOOK SET PHONE_NO = NULL WHERE (NAME = 'Lacey') ;
C) UPDATE ADDRESS_BOOK SET PHONE_NO = 'NULL' WHERE (NAME = 'Lacey') ;
D) UPDATE ADDRESS_BOOK SET PHONE_NO = NULL WHERE (NAME = 'Lacey') ;