Which statement is true? a) voltage varies throughout a series circuit. b) voltage remains the same throughout a series circuit.

Correct Answer is A

In a series circuit, the voltage across each resistive element is different and depends on the resistance of that element. However, the current throughout the series circuit is the same.

In a parallel circuit, the voltage is same across all the branches however the current in each branch is different and depends on the resistance of that branch. 

Points to Remember:
1) In series circuit current remains the same and voltage varies
2) In parallel circuit voltage remains the same and current varies

Where is the diagram? you need to be more specific in your question so we can you