When one light in a string of holiday lights goes out and the rest of the string also goes out, what type of current is used? a)open circuit b)series circuit c)combination circuit d)parallel circuit

That's a SERIES circuit.  The lights are wired in such a way that
there is only one path for the current to take, and the current for
any bulb must flow through all of them.  So if any bulb burns out
and current can't pass through it, then current can't flow through
ANY bulb, and they all go out. 

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Shania is trying to determine the oldest geologic unit on this map and the reason to why is she unable to do so is that  the units are all the same age.. when there is the same age, there will be no oldest geologic unit and that i cannot be credible.