Atoms or molecule after gaining of electron possesses negative charge and is known as anion.
For the given sets:
The given elements are alkali metals and have tendency to lose electrons easily and form cations.
The given elements are non-metals and are electronegative. So, they gain electrons easily and form anion.
Carbon has tendency to form bond by sharing of electrons, Sulfur has tendency to gain electrons and form anion whereas Lead has tendency to lose electron.
Potassium and Iron has tendency to lose electron and form cation whereas Bromine has tendency to gain electron to form anion.
Hence, from the given sets, all elements of set: 
have tendency to form anions in binary ionic compounds.
With a physical change you can actually see it change like ice turning into water, then with a chemical change you can't see it change, although within the molecules themselves they change which makes that possible.
Hope this helps!
Answer:
The reaction mentioned in the question is a decomposition reaction.
Explanation:
Decomposition reaction is a specific type of chemical reaction in which the reactant molecule undergo break down to generate its respective products.
NaCl ⇒ Na + Cl2
In the above reaction sodium chloride(NaCl) undergo decomposition or break down to generate Sodium(Na) and chlorine gas(Cl2).
Answer:
D
Explanation:
the H2O2 under go reduction to remove O2 and then forms water
