Materials suitable for making electromagnets should have low retentivity and low coercivity.

Retentivity (or remanence) is the ability of a magnetic material to retain its magnetism after the removal of the magnetizing force. For an electromagnet, we want this to be low, as we want the magnet to only be magnetic when current is flowing.

Coercivity is the ability of a magnetic material to resist becoming demagnetized. Again, for an electromagnet, we want this to be low, as we want to easily turn off the magnetism when the current is removed.

So, the correct option is :

Option B: Low retentivity and low coercivity.