The diagram depicts a cell linked to three resistors $R_1$, $R_2$ and $R_3$. A student places an ammeter at position 1 first, then at positions 2, 3 and 4 one after another. At which positions does the ammeter read the current in $R_1$?
- A1, 2 and 4
- B1 and 2 only
- C3 only
- D4 only