which TWO ways can this be changed to 2GB (2147483648 Bytes) on a running system?

It is possible to configure kernel parameters at runtime (e.g. the maximum size of the shared memory segment (shmmax)). In which TWO ways can this be changed to 2GB (2147483648 Bytes) on a running system?

A.
Edit /etc/shmmax and set the parameter to 2147483648.

B.
sysctl shmmax=2147483648.

C.
sysctl kernel.shmmax=2147483648

D.
echo 2147483648 > /proc/sys/kernel/shmmax

E.
export kernel.shmmax=2147483648