The desirable properties of core of a transformer are

The correct answer is Option (3) → High permeability and low hysteresis loss

The core of a transformer must link as much of the primary's flux as possible with the secondary, and it must waste as little energy as possible while it is magnetised and demagnetised every cycle.

A high permeability concentrates the magnetic flux in the core, so almost all of it links both coils. A low hysteresis loss keeps the energy lost as heat in each cycle of the alternating current small. Soft iron has both properties.

NCERT (2026-27):
Transformers – “… (iv) Hysteresis: The magnetisation of the core is repeatedly reversed by the alternating magnetic field. The resulting expenditure of energy in the core appears as heat and is kept to a minimum by using a magnetic material which has a low hysteresis loss.”