Question

The internet may best be compared to a/an

Answer 1

It could be compared to a brain :). Each computer is a neuron and the internet connections between them are the synapses that combine them and transfer information. 

This is indeed how some people think about it and it is quite an interesting idea when you think about it because when you graphically represent big amounts of computers and the internet connections between them, you would get something that looks very similar to a brain.