单项选择题 A user is unable to view any DVDs on their laptop which has a DVD-ROM drive installed. After further investigation, the technician realizes that there is not any DVD-ROM or CD-ROM available under the My Computer utility. Which of the following system utilities would MOST likely be used to identify and resolve this issue?（）

单项选择题 A system administrator has disabled USB ports after experiencing several virus outbreaks. A user needs to transfer several extremely large work related files from their home desktop computer to their work desktop computer. Which of the following will allow the user to transfer the needed files?（）

单项选择题 Which of the following commands will make exact duplicates of files and directory trees?（）