Which option to mount.cifs specifies a file containing the user name, password, and domain for authentication?

The option that specifies a file containing the user name, password, and domain for authentication when mounting a CIFS share is indeed credentials. This option allows users to store sensitive authentication information in a separate file, making it more secure and convenient than entering them directly in the command line. By providing the path to a credentials file, you can include parameters like the username, password, and domain, which are necessary for the mounting process.

Using a credentials file helps to enhance security by preventing sensitive information from being exposed in the command history or to other users on the system. The format of the credentials file typically follows a simple structure where each line contains one parameter in the form of "key=value," making it easy to read and edit.

Other options like authfile, secfile, and passfile do not exist as recognized parameters for mount.cifs in the way that the credentials option does, which reinforces why credentials is the correct choice for storing authentication details in a secure manner while mounting CIFS shares.