Which one of the following sets of compounds correctly illustrates the law of reciprocal proportions?

What weight of $BaCl_2$ is required to react with $24.4 \ g$ of sodium sulfate to produce $46.6 \ g$ of barium sulfate and $23.4 \ g$ of sodium chloride (in $g$)?

Among the following pairs of compounds,the one that illustrates the law of multiple proportions is

Which of the following sets of compounds illustrates the Law of Multiple Proportions?

The following data are obtained when dinitrogen and dioxygen react together to form different compounds:

Mass of dinitrogen	Mass of dioxygen
$(i) \ 14 \ g$	$16 \ g$
$(ii) \ 14 \ g$	$32 \ g$
$(iii) \ 28 \ g$	$32 \ g$
$(iv) \ 28 \ g$	$80 \ g$

$(a)$ Which law of chemical combination is obeyed by the above experimental data? Give its statement.
$(b)$ Fill in the blanks in the following conversions:
$(i) \ 1 \ km = \dots \ mm = \dots \ pm$
$(ii) \ 1 \ mg = \dots \ kg = \dots \ ng$
$(iii) \ 1 \ mL = \dots \ L = \dots \ dm^{3}$

Which of the following pairs of substances illustrates the Law of Multiple Proportions?