Which of the following does not give oxygen on heating?

$Fe$ is made passive by

The stable bivalency of $Pb$ and trivalency of $Bi$ is

Nitrogen can be obtained from air by removing

When orthophosphoric acid is heated to $600\,^oC$,it forms .................. .

Which is the correct sequence in the following properties? For the correct order mark $(T)$ and for the incorrect order mark $(F)$.
$(a)$ Lewis acidity order : $SiF_4 < SiCl_4 < SiBr_4 < SiI_4$
$(b)$ Melting point : $NH_3 > SbH_3 > AsH_3 > PH_3$
$(c)$ Boiling point : $NH_3 > SbH_3 > AsH_3 > PH_3$
$(d)$ Dipole moment order : $NH_3 > SbH_3 > AsH_3 > PH_3$