Answer:
Option 1, Cl is reduced and gains electrons
Explanation:
HClO₃ → HClO₂
In HClO₃, chlorine acts with +5 in the oxidation state
In HClO₂,, chlorine acts with +3 in the oxidation state.
The state has been reducted, so the Cl has been reduced. As it was reduced, it means that has won e⁻, in this case 2
Cl⁻⁵ → Cl⁻³ + 2e⁻
Both create energy. Both require atoms.
Fission is ripping the atoms apart, fusion is forcing them together. Fission takes less energy because it's easier to rip unstable atoms apart but pushing two atoms that have similar charges together is extremely hard. Fission is currently mainstream on earth, but fusion is known for taking place within stars.