Which word best matches the definition 'a source or supply of something'?

• A. resource
• B. revenue
• C. retain
• D. reverse

Answer: (A)

A resource is something that can be drawn on to help meet a goal—it's a source or supply you can rely on. The term covers things like natural resources such as water or minerals, financial resources, or human resources—anything you can use as a stockpile to accomplish tasks.

That fits the definition exactly because a resource describes a usable supply, rather than an action or outcome. For contrast, revenue means income or earnings, not a stock you draw from; retain is a verb meaning to keep, and reverse means to move backward or undo.