The correct option is A Increases
Generally, greater the number of unpaired electrons, higher is the melting point.
Similary, greater the number of unpaired electron, stronger will be the bonding and higher will be the boiling point.
Thus, melting and boiling point of 3d metals rise to a maximum at d5 (except for anomalous values of Mn) and then, fall regularly as the atomic number increases.
Hence, option (a) is correct.