Comprehensive and Detailed In-Depth Explanation: Ransomware is a type of malware that encrypts files and demands payment (usually in cryptocurrency) to decrypt them. * B. Keylogger - Tracks keystrokes but does not demand payment. * C. Cryptomining - Uses system resources to mine cryptocurrency without the user's consent. * D. Rootkit - Hides malicious software but does not demand payment. Reference: CompTIA A+ 220-1102, Objective 2.5 - Common Security Threats