Answer:
2Na⁺ (aq) and 2OH⁻(aq)
Explanation:
Spectator ions:
Spectator ions are those ions which are same on both side of chemical reaction. These ions are same in the reactant side and product side. Their presence can not effect the chemical equilibrium that's why when we write the net ionic equation these ions are neglect or omitted.
Given ionic equation:
Ba⁺²(aq) + 2OH⁻(aq) + 2Na⁺ (aq) + CO²⁻₃(aq) → BaCO₃(s) + + 2Na⁺ (aq) + 2OH⁻(aq)
In given ionic equation by omitting the spectator ions i.e, 2Na⁺ (aq) and 2OH⁻(aq) net ionic equation can be written as,
Net ionic equation:
Ba⁺²(aq) + CO²⁻₃(aq) → BaCO₃(s)
is there supposed be a picture with the question?
Answer:
C. Double Replacement
Explanation:
A. Wrong because SR uses a compound and element. This equation is a compound and compound.
B. Wrong because it does not have O2 in the formula. All combustion reactions must have O2.
C. Correct because it is a compound reacting with a compound.
D. Wrong because the reactants did not form a single product. ex. (x + y > xy)
E. Wrong because the equation did not start with a single compound and break down. ex. (xy > x + y)
Answer:

Explanation:
You can put that equation into a program like desmos on your browser and take a screenshot or use windows snippet tool.
Equation of a Wave: y = Acos(((2*pi)/B)x)
or

A = Amplitude
B= Wavelength