What is the cause of this issue?

Scenario: A Citrix Architect needs to assess a Citrix Gateway deployment that was recently completed by a customer and is currently in pre-production testing. The Citrix Gateway needs to use ICA proxy to provide access to a Citrix Virtual Apps and Citrix Virtual Desktops environment. During the assessment, the customer informs the architect that users are NOT able to launch published resources using the Gateway virtual server.

Click the Exhibit button to view the troubleshooting details collected by the customer.

What is the cause of this issue?
A . The Secure Ticket Authority (STA) servers are load balanced on the Citrix AD
C . The required ports have NOT been opened on the firewall between the Citrix Gateway and the Virtual Delivery Agent (VDA) machines
D . The StoreFront URL configured in the Citrix Gateway session profile is incorrect
E . The Citrix License Server is NOT reachable

Answer: A