Diagram 1 shows a lamp that is connected to a supply by means of two switches. While repairs are being carried out, an electrician accidentally swaps the connections $X_1$ and $Z_1$, so that $Z_1$ is joined to the supply and $X_1$ to the other switch $Z_2$, as shown in diagram 2. Which switch positions will now make the lamp light?
- A$X_1$ to $Y_1$ and $X_2$ to $Y_2$
- B$X_1$ to $Y_1$ and $X_2$ to $Z_2$
- C$X_1$ to $Z_1$ and $X_2$ to $Y_2$
- D$X_1$ to $Z_1$ and $X_2$ to $Z_2$