What happens to sulfur in the following unbalanced equation?

$H_{3}As{O}_4+H_{2}S{H}_{3}As{O}_3+S+H_{2}O$

a$.$ oxidized from $-2$ to $0$

b$.$ oxidized from $0$ to $-2$

c$.$ reduced from $-2$ to $0$

d$.$ reduced from $0$ to $-2$

e$.$ Sulfur is neither oxidized nor reduced in this reaction.

In which compound is the oxidation number of vanadium different from the oxidation numbers of the other elements?

a$.K_3{V}_3{O}_9$

b$.VOS{O}_4$

c$.N{H}_{4}V{O}_3$

d$.V{O}_{2}Cl{O}_4$

e$.V_2{O}_5$

Which substance is the reducing agent in the following equation?

$Pb{O}_2+Pb+4H^{+}2P{b}^{2+}+2H_{2}O$

a$.Pb$

b$.Pb{O}_2$

c$.H^{+}$

d$.P{b}^{2+}$

e$.H_{2}O$

$17.$ Which element is reduced in the following reaction?

$2Au+12H^{+}+3C{l}^{-}+3N{O}_3^{-}6H_{2}O+3$NOCl$+2A{u}^{3+}$

a$.$ chlorine

b$.$ nitrogen

c$.$ gold

d$.$ oxygen

e$.$ hydrogen

$18.$ The oxidation number of chromium $(Cr)$ in the dichromate ion $(C{r}_2{O}_7^{2-})$ is

a$.+2$

d$.+7$

b$.+4$

e$.-2$

c$.+6$

$19.$ Manganese $(Mn)$ has an oxidation number of $+6$ in

a$.Mn{O}_4^{2-}$

d$.$

b$.M{n}^{2+}$

e$.Mn{O}_2$

c$.MnC{l}_3$

$20.$ The oxidation number of sulfur $(S)$ in $N{a}_{2}S{O}_3$ is

a$.+6$

d$.+2$

b$.+4$

e$.0$

c$.+3$