System Hardening for Security

Can you answer this sample Security+ question on hardening? Q. Your organization wants to improve the security posture of internal database servers and protect against zero-day vulnerabilities. Of the following choices, what provides the BEST solution? A. Opening ports on a server’s firewall B. Disabling unnecessary services C. Keeping systems up to date with current patches D. Keeping systems up to date with current service packs

You can view the answer and explanation here.