What might you unknowingly download through free software that tracks your online activity?

The correct answer is adware. Adware is a type of software that automatically displays or downloads advertisements to a user's computer, often without their explicit consent. When you install free software, it may come bundled with adware that tracks your online activity to deliver targeted advertisements. Adware collects data on your browsing habits, which helps it generate revenue for its developers through advertising. This kind of software often goes unnoticed because it can be included in the terms of service or installation agreements that users frequently overlook.

Spyware, while also a possibility in free software, is typically more malicious and focused on collecting personal information without the user's knowledge to transmit it to third parties. Malware is a broader term encompassing various types of harmful software, including viruses and worms, which can disrupt or damage the system. Ransomware, on the other hand, is a very specific kind of malware that locks or encrypts files and demands payment for their release, which is usually not bundled with free applications as adware might be. Therefore, adware is the most likely candidate that can track your online activity among common free software downloads.