The correct answer is option C: The molecular formulas for the substance(s) on the left side of the equation and on the right side of the equation are identical. This means that there was not a chemical change, but a physical one.
In this concrete example, what happened was a <em>change of states of matter</em>: from liquid (l) to solid (s).
Other reactions have different molecular formulas on both sides of the equation, thus they represent chemical changes.
Due to we have total number of 6 carbons and one of them is the carboxylic group and we need to draw 2 methyl groups on the same carbon so the longest chain must be 4 carbons + 2 methyl branches and also these branches must be in carbon two and carbon three as follow: