Secondary current of a step-down transformer is less than its primary current.
A transformer is a static device so it has no mechanical losses. A transformer only transforms the voltage and the current and the frequency remains same during the transformation process. The power on primary side of an ideal transformer is equal to the power on the secondary side. It the transformer is step-down then the voltage on secondary side must be less than the voltage on its primary side which means that the current on secondary side must be higher than the current on its primary side.
B The frequency does not change in transformation action.
C A transformer has no mechanical losses.
D The power on primary side of an ideal transformer is equal to the power on secondary side.