In a cloud environment, it is crucial to have redundancy in all network functions to avoid single points of failure and ensure high availability. The correct answer is 'Load balancers' as they play a key role in distributing traffic across multiple servers to provide continuous service availability, even if one or more servers fail. 'Switches' and 'Routers' are also important, but their failure typically does not result directly in the loss of service as long as there is redundancy in place. 'DNS Servers' are a critical part of the internet infrastructure, but they are generally designed with redundancy, and their failure is usually related to wider issues than the context of a single cloud environment's high availability.