Concept:Paramagnetism arises from the presence of unpaired electrons in an atom or ion.
Explanation:In d-block elements, the d-orbitals are partially filled.
These partially filled d-orbitals contain unpaired electrons.
When such a substance is placed in a magnetic field, the unpaired electrons align with the field and produce attraction.
This attraction is called paramagnetism.
Paired electrons, on the other hand, give rise to diamagnetism, which is repelled by a magnetic field.
Hence, the paramagnetic nature of d-block elements is due to unpaired electrons present in the partially filled d-orbitals.
Answer:Option B: contain unpaired electrons in the partially filled 3d-orbital.