Which of These Would Be an Example of a DDoS

Which of these would be an example of a DDoS attack?

A) An extortion attempt where hackers threaten to reveal names and social security information stolen from medical records databases
B) Overloading a popular social networking site with inbound messages in order to shut down access to the site
C) Launching a targeted phishing campaign on a department of defense or other surveilance network.
D) Stealing proprietary data directly from mobile phones using a distributed network of difficult-to-trace online services.
E) Launching tough-to-track click-fraud efforts