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Question 17 (4 points) Listen Deadlock cannot happen if locks are used to prevent concurrent update problems. 1) True 2) False Question 18 (4 points) Listen In the mirrored databases" backup and recovery technique, two copies of the entire database are maintained and both are updated simultaneously. 1) True 2) False Question 20 (4 points) Listen A proxy server is firewall software that resides in the Web server. 1) True 2) False Question 21 (4 points) Listen The lost update problem can occur when 1) two users are trying to retrieve the same data simultaneously 2) one user is trying to retrieve data and another user is trying to update the same data simultaneously 3) two users are trying to update the same data simultaneously 4) All of the above. 5) None of the above