Brightest bulb

Electricity and Magnetism Level 2

Jane connected four identical light bulbs in a circuit as shown above. She observes that the brightness of bulb $A$ varies if some of the switches are closed. In which case will bulb $A$ burn brightest?

\text{When all of }S_1, S_2, S_3

\text{ are open.}

\text{When } S_1, S_2\text{ are closed }

\text{with }S_3\text{ open.}

\text{When } S_1\text{ is closed }

\text{with }S_2, S_3\text{ open.}

\text{When all of }S_1, S_2, S_3

\text{ are closed.}