The run keyword executes commands using the default shell unless a different shell is specified. Since the commands shown are Python statements, the step must define shell: python so GitHub Actions interprets the script using Python instead of Bash, PowerShell, or another default shell. Option D is therefore correct.
Option A is invalid because with: is used to pass inputs to actions, not to define the interpreter for a run command. Option B would execute the text as Bash and fail because import os is not Bash syntax. Option C only changes the working directory and does not change the shell. This exam topic checks workflow syntax, shell selection, and step-level command execution.