An issue was discovered on a testing branch of a Git repository. A file was inadvertently modified and needs to be reverted to the master branch version. Which of the following is the BEST option to…

`git branch -b master file` attempts to create a new branch from a file, which is syntactically incorrect and not for reverting files.

`git merge master testing` would attempt to integrate changes between the two branches, not revert a single file to a previous state from another branch.

`git stash branch master` creates a new branch from a stash entry, which is unrelated to restoring a file from another existing branch.

The `git checkout <branch> -- <file>` command allows you to discard local changes for a specific file or replace it with the version from a specified commit or branch. Using `git checkout master -- file` will replace the `file` in the current `testing` branch with the version it has in the `master` branch.