Answer:
Using Network Access Control Lists (ACL) to allow/deny traffic based on application IP addresses
Explanation:
ALL Network Access Control List has has distinct inbound and outbound rules.
Each of these rules are configured to either allow or deny traffic.
This is the best and easiest way to achieve the task at hand.
The Network ACL will be configured to allow inbound and outbound traffic for Application A to send and receive requests and only inbound traffic will be allowed for Application B to receive requests only from A