A systems administrator needs to reconfigure a Linux server to allow persistent IPv4 packet forwarding. Which of the following commands is the correct way to accomplish this task?

A. echo 1 > /proc/sys/net/ipv4/ipv_forward
B. sysctl -w net.ipv4.ip_forward=1
C. firewall-cmd –enable ipv4_forwarding
D. systemctl start ipv4_forwarding