The correct option is A Arabinose
Monosaccharides are made up of a single unit of sugar. The monosaccharides are called triose, tetrose, pentose, hexose or heptose based on the number of carbon atoms in them. Glucose and fructose are hexose sugars made up of six carbon atoms. Galactose is a tetrose or four carbon sugar. Arabinose is a five carbon sugar or pentose sugar.