Answer:
Fructose
Step-by-step explanation:
A ketose is a monosaccharide containing one ketone group (RCOR) per molecule.
This means to identify a ketose, one has to look for the ketone group in the structural formuar of the compound.
Mannose - This is an aldose. It contains the aldehyde functional group.
Galactose - This is an aldose. It contains the aldehyde functional group.
Fructose - This is a keose. It contains the Ketone Functional group.
Glucose - This is an aldose. It contains the aldehyde functional group.