The number of reactions which give $S{O}_2$ gas are:   

a)   $Cu+conc.H_{2}S{O}_4\to$
b)   $Zn+dil.H_{2}S{O}_4\to$
c)   $S+H_{2}S{O}_4\to$
d)   $Fe{S}_2+O_2\to$
e)   $NaHS{O}_3+dil.H_{2}S{O}_4\to$
f)   $H_{2}S{O}_4+PC{l}_5\to$
g)   $S{O}_{3\left(aq\right)}^{-2}+2H_{\left(aq\right)}^{+}\to$

(a)   $Cu+conc.H_{2}S{O}_4\to CuS{O}_4+S{O}_2+H_{2}O$
(b)   $Zn+dil.H_{2}S{O}_4\to ZnS{O}_4+H_2$
(c)   $S+H_{2}S{O}_4\to 3S{O}_2+H_{2}O$
(d)   $4Fe{S}_2+11O_2\to 2F{e}_2{O}_3+8S{O}_2$
(e)   $NaHS{O}_3+dil.H_{2}S{O}_4\to NaHS{O}_4+S{O}_2+H_{2}O$
(f)   
G) $S{O}_{3\left(aq\right)}^{-2}+2H_{\left(aq\right)}^{+}\to H_2{O}_{\left(l\right)}+S{O}_{2\left(g\right)}$