Two terminal devices circuit puzzle

Hi I came across the following puzzle which involves circuits and two terminal devices but i think it's basically a mathematical puzzle. But
i am unable to understand it.
In any circuit containing only "two terminal" devices we can always find two "links" whose removal (not simultaneous)
still left all the components connected to each other by wires.
a hint was also given : consider an unplugged toaster as a valid circuit in this puzzle.
I am unable to understand what is a circuit with "two terminal" devices and what are "links" in it.
Can anyone give an example of such a circuit in which the above property holds.
I think this problem can be converted into graphs. But i dont know how if it is possible?
Please help.
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