Formula Calcium chroride:

hope this helps!.
Answer:
Option C. Gain 1 electron
Explanation:
Valence electron(s) are the electron(s) located on the outermost shell of an atom. Valency is simply defined as the combining power of an atom.
Chlorine (Cl) atom has 7 valence electron. This implies that Cl needs just one electron to complete it's octet configuration. It will be difficult for Cl to lose any of it's valence electron(s). Cl can either gain or share 1 electron to become stable.
Thus, considering the options given in the question above, option C gives the correct answer to the question.
Answer: Wax
Explanation:
Density is defined as the mass contained per unit volume.

Usually solids are more denser than liquid, as molecules in solid are more strongly packed and thus have more mass per unit volume.
Liquids on the other hand contain molecules which are less tightly bound and thus thus contain less mass per unit volume as compared to solid.
Example: Solid wax is more denser than liquid wax.
Answer:
B. The only planet to support life.
Explanation:
Combination or synthesis reaction