The reaction corresponding to 1st option is Fe + S - > FeS
Reaction corresponding to 2nd option is 2Hg + O₂ - > 2HgO
Reaction corresponding to 3rd option is Ca + 2 H₂O - Ca(OH)₂ + H₂.
Reaction corresponding to 4th option is H₂ + Cl₂ - > 2 HCl.
<h3><u>Explanation:</u></h3>
The iron and sulphur undergoes a redox reaction where the iron gets oxidized to ferrous ion and Sulphur gets reduced to sulphide ion. Its an addition reaction as well.
The mercury and oxygen undergoes a redox reaction which makes the oxygen to oxide ion and mercury to mercuric ions. Its an addition reaction as well.
The calcium and water undergoes a displacement reaction where the calcium removes the hydrogen from water forming calcium hydroxide and hydrogen gas.
The hydrogen and chlorine undergoes an addition reaction forming hydrogen chloride. Its also a redox reaction as well.
