The correct answer is:
DDoS attacks utilize many computers for making bogus requests, instead of just one.
In a regular Denial of Service (DoS) attack, a single source (one computer) is used to flood a target system with unnecessary requests, overwhelming it and rendering it unavailable. In contrast, a Distributed Denial of Service (DDoS) attack employs multiple compromised computers (often part of a botnet) to generate a large volume of requests, making it more difficult to mitigate and defend against than a standard DoS attack.