A Security Classification Guide (SCG) is: Select one: a. A document that defines how to mark a classified document. b. A document that provides basic guidance and regulatory requirements for the DoD Information Security Program. c. An existing classified document, from which information is extracted, paraphrased, restated, and/or generated in a new form for inclusion in another document. d. A collection of precise, comprehensive guidance about specific program, system, operation, or weapon system elements of information to be classified.

a. A document that defines how to mark a classified document.

Explanation:

The main purpose of Security Classification Guide (SCG) is to provide a uniform means of classifying same information in order to ensure certain level of protection is reached for that particular information.

Security Classification Guides (SCG) becomes invalid, when the information prescribed in the guide no longer  requires protection, or the information has been included in another guide.

A properly constructed Classification Guide will enable accurate classification and improve user derivative classification decisions.

A collection of precise, comprehensive guidance about specific program, system, operation, or weapon system elements of information to be classified

Explanation:

you have to first get good enough where you are an ace or master, then some of the creators could make you a mod. (this is pretty hard to do though)