Explanation:
Simple replacement reactions are those that occur between a compound substance (made up of more than one chemical element) and a simple substance (made up of only one type of chemical element), giving rise to another simple substance and another compound.
Generically, we have:
A + CD → AC + D
In this question, we have the following choice as a single replacement reaction:
Mg + FeS → Fe + MgS
Answer: A. Mg + FeS → Fe + MgS
