A customer implements Cloud Identity-Aware Proxy for their ERP system hosted on Compute Engine. Their security team wants to add a security layer so that the ERP systems only accept traffic from Cloud Identity-Aware Proxy. What should the customer do to meet these requirements? 

Answer options:

A. Make sure that the ERP system can validate the JWT assertion in the HTTP requests.
B. Make sure that the ERP system can validate the identity headers in the HTTP requests.
C. Make sure that the ERP system can validate the x-forwarded-for headers in the HTTP requests.
D. Make sure that the ERP system can validate the user`s unique identifier headers in the HTTP requests.

A