So, if we want to track something that was spreading through a network, what we ideally would like to do is to set up sensors on the central individuals within the network, including node A, monitor those people that are right there in the middle of the network, and somehow get an early detection of whatever it is that is spreading through the network.
如果我们要追踪 在网络中传播的事物， 理想情况下我们会想设置感应器 在网络的中心人物上， 包括结点A, 以此来观察网络中心的人们的活动， 从而能够做到及早探测 正在网络中传播的东西。