The answer would be B, flapping ability.
There are several various of expressing concentration. For instance, mass percent, volume percent, Molarity, Normality, Molality, etc.
In present case, weight of solute and solvent are given, so it will be convenient to express concentration in terms of mass percent.
Given: weight of solute (Ca2+) = 8500 g
weight of solvent (water) = 490 g.
Therefore, mass of solution = 8500 + 490 = 8990 g
Now, mass percent =

=

= 94.55 %
Answer: Concentration of calcium ions is in this solution is 94.55 % (w/W)
Your answer is A my friend as the atomic number of an atom is determined by the number of protons
Displcement reaction. metal added to solutions containing metal that is less reactive would have visible reaction while less reactive metal will have no visible reaction. Eg, if copper is added to Mgcl2 andZnCl2, there will be no visible reaction. If Mg is added to CuCl2, blue solution will fade to form colourless solution and a reddish brown ppt of Cu will be formed.
I’m thinking it’s gold because lead isn’t with cooper meaning that if u switch lead with cooper it won’t work at all .