The Aruba CX 6400 switch is a modular switch that supports high-performance and high-density Ethernet switching for campus and data center networks. One of the features that distinguishes the Aruba CX 6400 switch from most typical campus switches is virtual output queueing (VOQ). VOQ is a technique that implements large ingress packet buffers on each port to prevent head-of-line blocking and packet loss due to congestion2. VOQ allows each port to have multiple queues for different output ports and prioritize packets based on their destination and QoS class2. VOQ enables the Aruba CX 6400 switch to achieve high throughput and low latency for various traffic types and scenarios.References: 2
https://www.arubanetworks.com/assets/ds/DS_CX6400Series.pdf

Two parts of the solution for these requirements are Option C and Option E.
Option C is a part of the solution because it defines a policy-based routing action list named route_test, which specifies the next hop IP address as 10.1.1.253 for the matching traffic. This is the new default route that the user wants to use for the subnet 10.2.250.0/24.The interface null parameter indicates that the traffic will be routed to the next hop without using a specific interface1.
Option E is a part of the solution because it applies the policy-based routing action list route_test to the VLAN interface 250, which has an IP address of 10.2.250.1/24. This is the subnet that the user wants to test the new default route for.The apply policy command enables policy-based routing on the interface and associates it with the action list2.
Option A is not a part of the solution because it defines a policy-based routing action list named route_test, but does not specify the next hop IP address as 10.1.1.253, which is the new default route that the user wants to use. Instead, it specifies a next hop IP address of 10.1.1.254, which is different from the requirement.
Option B is not a part of the solution because it defines a policy-based routing action list named route_test, but does not specify any next hop IP address at all, which is necessary for policy-based routing to work. Instead, it specifies an interface null parameter without any IP address, which is invalid.
Option D is not a part of the solution because it applies the policy-based routing action list route_test to the VLAN interface 200, which has an IP address of 10.2.200.1/24. This is not the subnet that the user wants to test the new default route for, but a different subnet that should not be affected by this change.

According to the Aruba Documentation Portal1, the ArubaOS-CX switch supports various features to control the ingress traffic on specific ports, such as rate limiting, QoS shaping, and access control. These features can help reduce the impact of excessive broadcast traffic on the network performance and availability.
This is because rate limiting is a feature that allows you to limit the inbound or outbound traffic on a port based on a percentage of the port capacity or a fixed amount of bytes per second. Rate limiting can help prevent broadcast storms by reducing the amount of broadcast packets that enter or leave a port
https://www.arubanetworks.com/techdocs/central/latest/content/nms/aos-cx/cfg/conf-cx-access-control.htm 2:
https://community.arubanetworks.com/blogs/esupport1/2021/02/08/broadcast-storm-containment-in-aruba-pvos-

According to the Aruba Documentation Portal1, 802.1X is a standard for port-based network access control that uses a RADIUS server to authenticate and authorize wireless clients. 802.1X can be configured in different modes, such as bridge mode, tunnel mode, or split tunnel mode.
Option C: GRE tunnel
This is because option C shows how to configure an SSID in tunnel mode with the default AP-group settings on an Aruba switch. In tunnel mode, all client traffic from the access points is tunneled back to the controller and the controller would in turn put the client traffic onto the network2. The GRE protocol is used to encapsulate and decapsulate the traffic between the access points and the controller3.
Therefore, option C is correct.
1:
https://www.arubanetworks.com/techdocs/AOS-CX/10.06/HTML/5200-7696/GUID-581D2976-694B-46C7-849
https://community.arubanetworks.com/discussion/bridge-and-tunnel-mode 3:
https://www.twingate.com/blog/ipsec-tunnel-mode

The show aaa authentication port-access interface all client-status command displays the status of all clients authenticated by port-based access control on all interfaces. The output includes the MAC address, user role, VLAN ID, and session timeout for each client. This command can be used to examine information on which role the guest user has been assigned by the AOS-CX switch.References:
https://techhub.hpe.com/eginfolib/Aruba/OS-CX_10.04/5200-6692/GUID-9B8F6E8F-9C7A-4F0D-AE7B-9D8E