Answer : The light rays are bent and refraction will occur - B.
Chemical equation represents a redox reaction :
2Li + MgCl₂ → 2LiCl + Mg
<h3>Further explanation</h3>
The oxidation-reduction reaction or abbreviated as Redox is a chemical reaction in which there is a change in oxidation number
Reaction
2Li + MgCl₂ → 2LiCl + Mg
Oxidation is an increase in oxidation number, while reduction is a decrease in oxidation number.
Oxidation

Reduction

Answer:
Catalysts
Explanation:
Catalysts lower the aviation energy.
Those would be called indicators , simply google them and you should find many. I'll leave some examples "bromophenol blue" "Methyl red" and "phenol red".