Explain in a short sentence how you can tell if a reaction is a single replacement
reaction.

Explanation:

The reaction can be said to be a single replacement reaction if one substance in a chemical reaction is replacing another one.

For example:

            A + BC →  AC + B

In such reactions there is a replacement of a metallic ion in solution by a metal atom higher in the activity series than the metal in solution.

The relative positions of the two elements in the activity series provides the driving force for a single replacement reaction. If one element that is to replace another in a compound is more active, the reaction will occur. If it is less reactive, there will be no reaction.