Question: A circuit is connected as shown. All light bulbs are identical. When the switch in the circuit is closed illuminating bulb #4, which other bulb(s) also become brighter? A) Bulb #1 only  B) Bulb #2 only  C) Bulbs #2 and #3 only  D) Bulbs #1, #2, and #3. Please choose an answer from [A, B, C, D].
Answer: A