$R_{A}$ and $R_{B}$ are the input resistances of circuits as shown below. The circuits extend infinitely in the direction shown. Which one of the following statements is TRUE?
1. $R_{A}=R_{B}$
2. $R_{A}=R_{B}=0$
3. $R_{A}< R_{B}$
4. $R_{B}= R_{A} /(1+R_{A})$