单项选择题 Which of the following cable types is intended to be used on short distances and is immune to anytype of interference?（）

单项选择题 Which of the following protocols requests membership to a multicast group?（）

单项选择题 A small amount of spoofed packets are being sent across a network and a large amount of reply packets are being sent back to the network resource. Which of the following BEST describes this security threat?（）