Which three methods might be used to change kernel parameters, thereby modifying the values for running system?

[answerhappygod]

Which three methods might be used to change kernel parameters, thereby modifying the values for running system?

A. Using the echo command to write values to specific files in the /sys directory
B. Issuing the sysct1 -w command to write values to specific files in the /proc/sys directory
C. Issuing the sysct1 -w command to write values to specific files in the /sys directory
D. Adding to or modifying parameters in /etc/sysct1.conf and issuing the sysct1 -p command E. Using the echo command to write values to specific files in the /proc/sys directory