A fixed resistor is attached to the secondary coil of a step-down transformer. The transformer is 100% efficient. The variable resistor is altered so that the current in the fixed resistor falls by $0.25\,\text{A}$. What is the change in the current in the primary circuit?
- AIt decreases by $0.25\,\text{A}$.
- BIt decreases by less than $0.25\,\text{A}$.
- CIt decreases by more than $0.25\,\text{A}$.
- DThere is no change.