Asynthesis reaction will produce a
element
compound
ion
atom

Answer;

A compound

Explanation;A synthesis reaction is a type of reaction in which reactants combine to form a single compound or one product. It may also refer to reactions where a compound is formed from its constituent elements.For example, compound water is made by combining elements oxygen and water; that is;  2H₂ + O₂ → 2H₂O. This a synthesis reaction where oxygen and hydrogen reacts to form a single compound water.

When a virus infects a host cell, it uses the cell's machinery to make copies of its own genetic material in a process called replication. finally, during the process of self-assembly, that protein shell and the copies of the virus's genetic material are assembled into new viruses.