The correct option is Filtering and scoring stages.

Filtering and scoring stages are the core phases the kube-scheduler uses to choose a node for a pod. In the filtering phase the scheduler removes nodes that cannot run the pod because of constraints like node selectors, taints and tolerations, resource requests, and affinity rules. In the scoring phase the scheduler ranks the remaining nodes using built in scoring functions such as resource balancing and topology awareness and then chooses the highest scoring node.

Prioritization and container image availability is incorrect because prioritization is an older term that maps to scoring and container image availability is validated by the kubelet or admission controllers rather than being a scheduler phase.

Preemption and PodDisruptionBudget checks is incorrect because preemption is a mechanism to make room for higher priority pods and it is not one of the primary node selection phases, and PodDisruptionBudgets govern voluntary disruptions and eviction policies rather than the scheduler scoring process.

Sharding and certificate signing is incorrect because those concepts are unrelated to pod scheduling. Sharding refers to data partitioning and certificate signing is part of cluster security and neither influences the scheduler node selection phases.

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