A User Is Accessing an EC2 Instance on the SSH

Multiple Choice

A user is accessing an EC2 instance on the SSH port for IP 10.20.30.40/32. Which one is a secure way to configure that the instance can be accessed only from this IP?

A) In the security group, open port 22 for IP 10.20.30.40
B) In the security group, open port 22 for IP 10.20.30.0
C) In the security group, open port 22 for IP 10.20.30.40/32
D) In the security group, open port 22 for IP 10.20.30.40/0