The diagram depicts an electrical circuit. Which statement is correct?
- AThe current reading on ammeter $A_1$ is the highest.
- BThe current reading on ammeter $A_2$ is the highest.
- CThe current reading on ammeter $A_3$ is the highest.
- DThe current readings on all three ammeters $A_1$, $A_2$ and $A_3$ are the same.