Burst workloads are a classic elasticity problem: you need large capacity for a short window, then very little capacity the rest of the week. The most cost-effective approach in a cloud-based Kubernetes environment is to scale infrastructure dynamically, matching node count to current demand. That's exactly what Cluster Autoscaler is designed for: it adds nodes when Pods cannot be scheduled due to insufficient resources and removes nodes when they become underutilized and can be drained safely. Therefore B is correct.
Option A can work operationally, but it commonly results in paying for a reserved "standing army" of nodes that sit idle most of the week-wasteful for bursty patterns unless the nodes are repurposed for other workloads. Taints/tolerations and nodeSelectors are placement tools; they don't reduce cost by themselves and may increase waste if they isolate nodes. Option D (PriorityClasses) affects which Pods get scheduled first given available capacity, but it does not create capacity. If the cluster doesn't have enough nodes, high priority Pods will still remain Pending. Option C (reserved instances or committed-use discounts) can reduce unit price, but it assumes relatively predictable baseline usage. For true bursts, you usually want a smaller baseline plus autoscaling, and optionally combine it with discounted capacity types if your cloud supports them.
In Kubernetes terms, the control loop is: batch Jobs create Pods → scheduler tries to place Pods → if many Pods are Pending due to insufficient CPU/memory, Cluster Autoscaler observes this and increases the node group size → new nodes join and kube-scheduler places Pods → after jobs finish and nodes become empty, Cluster Autoscaler drains and removes nodes. This matches cloud-native principles: elasticity, pay-for-what-you-use, and automation. It minimizes idle capacity while still meeting the completion deadline.