What is an efficient way to accomplish this?

As part of its recent efforts to improve brand recognition, Universal Containers had upgraded all of its Communities to use Lightning templates. The next step will be to unify the branding across all of these Communities.

What is an efficient way to accomplish this? Select one or more of the following:
A . Use a shared Bootstrap CSS file in all of the Communities
B . Ensure that all Communities are only using standard Lighting Components
C . Create a standard theme that is used in all of the Communities
D . Ensure that all Community managers use the same CSS standards in all pages

Answer: C