(a, b, d)

It results from the electrical attractions among positively charged metal ions and mobile, delocalised electrons belonging to the crystal as a whole.

In general, greater the number of (n–1)d and ns electrons, stronger is the resultant bonding.

Strength of metallic bond depend on the type of hybrid orbitals participating in metallic bonding.

As the size of atom increases the attraction between the positive part of the atom and delocalised electrons decreases and thus the strength of the metallic bond decreases.