Which of the following correctly uses a GitHub Actions expression to set an environment variable in a step?
Select an answer to reveal the explanation.
Short Explanation and Infographic
GitHub Actions expressions always live inside double curly braces prefixed with a dollar sign: ${{ expression }}.
Full explanation below image
Full Explanation
GitHub Actions expression syntax is '${{ <expression> }}'. The double curly braces delimit the expression context where you can access contexts (github, env, secrets, etc.), use functions (contains(), startsWith()), and perform comparisons. '$()' is command substitution in bash shell — not workflow YAML. Single curly braces '{github.actor}' is not recognized. '%variable%' is Windows cmd.exe syntax. The expression is evaluated by the GitHub Actions runner before the step executes, replacing the '${{ }}' token with the resolved value.