Final answer:
The correct answer is D) Enhanced network redundancy. EtherChannel combined with STP provides multiple paths without network loops, thereby increasing network resilience and avoiding single points of failure.
Step-by-step explanation:
When a network administrator connects two switches using EtherChannel technology and Spanning Tree Protocol (STP) is running, the end result will be D) Enhanced network redundancy. EtherChannel allows multiple physical links to be bundled into a single logical link, which provides benefits such as increased bandwidth and load balancing. With STP running, loops within the network are avoided, ensuring that there is no broadcast storm. The combination of EtherChannel and STP enhances the network's redundancy by providing multiple paths that can immediately be used in case one of the links fails, without causing loops in the network topology.