What is a software patch?

• A. A major rewrite of the entire system.
• B. A compilation of user documentation.
• C. A non-security related release schedule.
• D. An update to existing software to add functionality or to correct a defect.

Answer: (D)

A patch is a software update applied to existing software to fix defects or vulnerabilities, and sometimes to add small improvements or new functionality. It preserves your current system while addressing problems, rather than rewriting the whole program.

That’s why this option is correct: it describes updating software to correct defects and sometimes add functionality. The other ideas don’t fit—a major rewrite means replacing the whole system, a compilation of user documents isn’t software, and a release schedule is about timing rather than an actual update to the software.