A wire is inserted into a circuit. At $R$, the wire has cross-sectional area $A$, whereas at $S$ it is $\frac{1}{2}A$. The current in the wire is constant. Charge $Q$ passes point $R$ in a time $t$. What charge passes point $S$ in the same time $t$?
- A$\frac{1}{2}Q$
- B$Q$
- C$Q\sqrt{2}$
- D$2Q$