Using vi， you want to save changes to the file myfile with ：w!， but vi complains it cannot write to the file. Therefore， you want to check the write permissions on the file. To do this without leaving vi， you type：（）

A. kill-1 123
B. kill-9 123
C. kill-15 123
D. kill-17 123

A. tr ’\r\n’ " < userlist.txt > newlist.txt
B. tr -c ’\n\r’ " < newlist.txt > userlist.txt
C. tr -d \r¯ < userlist.txt > newlist.txt
D. tr \r¯\n¯ userlist.txt newlist.txt
E. tr -s ®^M’¡®^J’ userlist.txt newlist.tx

A. foo and bar would both be removed.
B. foo would be removed while bar would remain accessible.
C. foo would be removed， bar would still exist but would be unusable.
D. Both foo and bar would remain accessible.
E. You would be asked whether bar should be removed.