LFS211 - Question 15.1 iptables to "regulate" access

HenrikAreskoug

Hello,
Question 15.1 goes as follows:

How can access to services and ports be regulated? Select all answers that apply.

Surprisingly to me, option A; iptables is incorrect.
Please advise as to how that can be when I can "regulate" access to e.g. the service SSH by defining a rule such as:
iptables -A INPUT -p tcp --dport 22 -J ACCEPT

Thanks,
/Henrik