Question

Can you explain so I can understand

Answer 1

So, it's asking which is not needed for an electric circuit
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In that case, think of or google a picture of an electric circuit diagram. 
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Look at one and think of something that would not be needed for an electric circuit [ Based on the answer choices ] 
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If you need the answer, comment that and I will tell you.
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Glad I could help, and good luck!
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Answer 2

It would be insulator because an insulator kills electricity, it can't travel through it.