Answer:
Your answer should be B.) C, Si, Ge, Sn! I hope this helps you! :)
Balanced chemical reaction: 2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g).
KOH is inorganic compound p<span>otassium hydroxide, a strong base.
H</span>₂ is hydrogen gas.
In balanced chemical reaction number of atoms on both side of chemical reaction must be same. There are two potassium atoms, four hydrogen atoms and two oxygen atoms on both side of reaction.
We have to know the solubility of CaF₂.
The solubility of CaF₂ is: (c) 2.1 x 10-4 Molar
The general expression of solubility product of any sparingly soluble salt (having solubility S) with formula
is:
.
For the compound, CaF₂, x=1, y=2 So,
=
=4S³= 3.9 x 10-11 (Given)
S³=
S³=9.75 X 
S= 2.1 X
Molar