The balanced chemcial equation is B. So to do single, we need to look at where would Li stand on the metals chart (For my class we have a chart to see which element is the highest on the metals chart) . So since Li is higher, F needs to go with Li, leaving Ba alone.
A single replacement reaction is defined as the reaction where an element upon reaction with a compound tends to displace another element in that compound.
For example, is a single replacement reaction.
And, when number of atoms on reactant side equal to the number of atoms on product side then it is known as a balanced chemical reaction.
Thus, we can conclude that represents a balanced, single replacement chemical reaction.