The best option to describe where an attacker can purchase DDoS or ransomware services is the dark web. The dark web is an anonymous, untraceable part of the internet where a variety of illicit activities take place, including the purchase of DDoS and ransomware services. According to the CompTIA Security+ SY0-601 Official Text Book, attackers can purchase these services anonymously and without the risk of detection or attribution. Additionally, the text book recommends that organizations monitor the dark web to detect any possible threats or malicious activity.

Threat feeds, also known as threat intelligence feeds, are a source of information about current and emerging threats, vulnerabilities, and malicious activities targeting organizations. Security analysts use threat feeds to gather information about attacks and threats targeting their industry or sector. These feeds are typically provided by security companies, research organizations, or industry-specific groups. By using threat feeds, analysts can identify trends, patterns, and potential threats that may target their own organization, allowing them to take proactive steps to protect their systems.
Reference:
1. CompTIA Security+ Certification Exam Objectives (SY0-601): https://www.comptia.jp/pdf/Security%2B%20SY0-601%20Exam%20Objectives.pdf
2. SANS Institute: Threat Intelligence: What It Is, and How to Use It Effectively: https://www.sans.org-room/whitepapers/analyst/threat-intelligence-is-effectively-36367

Detailed Recovery Point Objective (RPO) is the maximum duration of time that an organization can tolerate data loss in the event of an outage. It identifies the point in time when data recovery must begin, and any data loss beyond that point is considered unacceptable.

Configuring the guest wireless network on a separate VLAN from the company's internal wireless network will prevent visitors from accessing company resources. Reference: CompTIA Security+ Study Guide: Exam SY0-601, Chapter 4