Irene is working on a series circuit for her science lab class. The circuit is made up of a battery, a light bulb, a switch, and connecting wires. When Irene flips the switch, the light bulb lights up. What did the switch do for the circuit?
a. The switch had no effect on the circuit.
b. The switch provided light energy to the bulb.
c. The switch produced the electricity for the circuit.
d. The switch completed the circuit.