Raffinose is a:

Hint: The Raffinose is a complex type of carbohydrate, contains three to ten saccharide units, it is alpha-galactosyl derivatives of sucrose that constitute an important form of transported carbon in some plants.

Complete step by step solution:
 To answer this question we have to know about the Raffinose. Since it contains three monosaccharide units. Raffinose is a trisaccharide. It provides glucose + fructose + galactose upon hydrolysis. It is primarily found in beans, cabbage, Brussels sprouts, broccoli, asparagus, and also in whole grains. Seeds, roots, and tubers of many plant species are also stored in these oligosaccharides. In addition to being a form of carbohydrate storage and transport, the Raffinose members play a role in tolerance of abiotic stress.
In plants, the binding of galactinol (a sugar alcohol) to sucrose generates raffinose. Raffinose has only twenty percent of sucrose's sweetening frequency. The prevailing carbohydrate translocated in the phloem is raffinose in the family’s Lamiaceae, Cucurbitaceae and Oleaceae. Raffinose oligosaccharides are formulated in specialized phloem companion cells, where the galactose units supplied by galactinol are added to sucrose gradually.
The major raffinose compounds are raffinose (trisaccharide) and stachyose (tetrasaccharide), but higher oligomers can also be found in some plants.

Note:
The low nutritional value of oligosaccharide compounds present in beans and other legumes has usually been regarded, as these foods account for indigestibility and the promotion of flatulence in humans and animals.