A scientist was testing an unknown chemical for the presence of various sugars and found that the only sugar present was the monosaccharide ribose. Which of the following molecules is most likely the unknown chemical?

The answer is; Benedict's reagent

It is used to test for reducing sugars. In presence of these sugars, the reagent, that is blue in color, turns different shaded of red (to brick red), depending on the amount of reducing sugars in the solution. It is important to note that the solution has to be heated.