Many factors must be taken into consideration: the children's personality and maturity, the amount of time the children will be alone, the safety of the neighborhood, ____(可以得到) of help in case of an emergency.

A. bash
B. ksh
C. tcsh
D. sh

A. chmod 500 /tmp/test.sh
B. chmod 501 /tmp/test.sh
C. chmod 700 /tmp/test.sh
D. chmod 007 /tmp/test.sh

A. chmod stu ./samplefile
B. chown stu ./samplefile
C. chown :stu ./samplefile
D. chmod :stu ./samplefile