Which statement is true about a Smurf attack？（）

• A、It sends ping requests in segments of an invalid size
• B、It intercepts the third step in a TCP three-way handshake to hijack a session
• C、It sends ping requests to a subnet， requesting that devices on that subnet send ping replies to a targetsystem
• D、It uses Trojan horse applications to create a distributed collection of "zombie" computers， which can beused to launch a coordinated DDoS attack