Final answer:
OpenVAS is the open-source vulnerability assessment engine among the options provided. It scans for known vulnerabilities and is licensed under the GNU General Public License (GPL). The correct answer is 3) OpenVAS.
Step-by-step explanation:
The open-source vulnerability assessment engine that scans for known vulnerabilities is OpenVAS. It is a software framework of several services and tools offering vulnerability scanning and vulnerability management.
All OpenVAS products are free software, and most components are licensed under the GNU General Public License (GPL).
Tools such as Nessus and Acunetix are proprietary, while Burp Suite has both a free version and a professional version, but they are not open-source like OpenVAS.
OpenVAS is a powerful tool that helps detect security issues in computer systems. It can scan for known vulnerabilities and helps identify potential risks that could be exploited by attackers.