‘H’ electronic configuration is  $1s^1$ and ‘Cl’ electronic configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^5$ 

I)  $H_2$ molecule formed by overlapping of two s-orbital’s of two hydrogen atoms.  So the type of bond is s - s overlapping.

II) $C{l}_2$ Molecule formed by overlapping of two $p_z$ orbital’s of two chlorine atoms.  So the type of bond is p – p overlapping.

III) HCl molecule formed by overlapping of one s-orbital of hydrogen atom and one  $p_z$orbital of chlorine atom. So the type of bond s – p overlapping.