The correct option is Configure a kubeconfig context that includes the target namespace using kubectl config set-context.

Configure a kubeconfig context that includes the target namespace using kubectl config set-context sets a default namespace inside the kubeconfig context so kubectl uses that namespace when you do not pass a namespace flag. This persists across shell sessions and makes it easy to switch workspaces by changing contexts rather than repeating the namespace on every command.

You apply this by setting the namespace on a context with the set-context action and then making that context active. Once the context is active kubectl will use the configured namespace by default and you will not need to add the namespace flag to each command.

Export an environment variable in your shell session that records the current namespace is incorrect because kubectl does not read a standard environment variable for the active namespace. You can create aliases or wrappers, but that is not a built in, reliable kubectl mechanism and it will not automatically work across different shells unless you persist it in your shell startup files.

Attempt to use a kubectl switch-namespace command to change namespaces temporarily is incorrect because there is no built in kubectl command with that name. There are third party utilities such as kubens that help switch namespaces, but they are not part of kubectl itself and so are not the expected answer on the exam.

Add the --namespace flag to every kubectl invocation to specify the namespace explicitly is technically valid but it is inefficient and error prone when you work across many commands and contexts. The question asks for the most efficient method and setting the namespace on the kubeconfig context is the preferred solution.

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