It is a.combination that is the correct answer i think
Given:
Concentration of titrant = 0.1000 M
Volume of titrant = 45 mL
The molarity of analyte depends on the amount of the analyte present in the titrated solution. If the amount of analyte is 20 mL, then its concentration is:
45ml * 0.10 M = C analyte * 20 ml
C analyte = 0.225 M
Answer: The correct formula is 
Explanation:
For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
Here magnesium is having an oxidation state of +2 called as 
cation and bromine 
is an anion with oxidation state of -1. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral .
The cations and anions being oppositely charged attract each other through strong coloumbic forces and form an ionic bond.
All chemical reaction between substances results into a chemical change. When two substances just like HCL and NaOH reacts with each other, NaCl means Sodium Chloride salt is formed.
The phenomenon like change in color, change in temperature, release of gas etc when happens ,then it means chemical change has been occurred. e.g
HCl +NaOH ----> NaCl +H2O.
