EIGRP does not require a hierarchical physical topology. It uses Diffusing Update Algorithm (DUAL) to provide loop prevention, and it supports Message-Digest Algorithm 5 (MD5) authentication. It can differentiate between internal and external routes, and uses a 32-bit metric.

EIGRP is a classless protocol that allows the use of variable length subnet masks (VLSM) and supports classless interdomain routing (CIDR) for allocation of IP addresses. The following are characteristics of EIGRP:
* Supports large networks due to high scalability
* Provides fast convergence using the Diffusing Update Algorithm (DUAL)
* Performs equal and unequal load balancing by default
* Supports variable length subnet masks (VLSM) and classless interdomain routing (CIDR)
* Is a hybrid routing protocol (distance-vector protocol) that also provides link-state protocol characteristics
* Is a classless protocol
* Sends partial route updates only when there are changes, reducing bandwidth usage for routing updates
* Has an administrative distance of 90 for EIGRP internal routes, 170 for EIGRP external routes, and 5 for EIGRP summary routes
* Is used only with Cisco platforms
* Provides support for IP IPX and AppleTalk protocols
* Can differentiate between internal and external routes
* Uses a 32-bit metric

EIGRP can load-balance up to four unequal cost paths. To do so, use the variance n command to instruct the router to include routes with a metric of less than n times the minimum metric route for that destination. The variable n can take a value between 1 and 128. The default is 1, which means equal cost load balancing.

The option stating that EIGRP requires a hierarchical physical topology is incorrect because EIGRP does not require or support a hierarchical routing topology.

The option stating that EIGRP uses Bellman-Ford algorithm to provide loop prevention is incorrect. EIGRP uses DUAL to provide loop prevention.