Which of these most likely represents a chemical change? water boiling
sugars digested by saliva
mud drying to dirt
ice cream melting

sugars digested by saliva.

Explanation:
An enzyme called salivary amylase helps in the breakdown of sugar into small particles. This enzyme affects the sugar for a small period of time in the mouth.
Once, salivary amylase reaches the stomach it becomes inactive because of the acid present in stomach. Further, this acid breaks the sugar molecules and these molecules are sent to the intestine for further reaction.
Thus, we can conclude that sugars digested by saliva is a chemical change.

Bacteria and fungi are the two types of decomposers.

Bacteria: Single-celled microorganisms that can exist either as independent (free-living) organisms or as parasites (dependent on another organism for life).

Fungi: A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms.