Any of a group of organic compounds that includes sugars, starches, cellulose, and gums and serves as a major energy source in the diet of animals; they are produced by photosynthetic plants and contain only carbon, hydrogen, and oxygen, usually in the ratio

1 : 2 : 1

Explanation:

Carbohydrates were originally referred to as 'hydrates of carbon' because they contained hydrogen, oxygen and carbon.

Sugars, starches, cellulose, and gums all belong to the class of carbohydrates.

They are represented by the general formula Cx(H2O)y, where x and y must be whole numbers.

Thus, Carbohydrates contain carbon, hydrogen and oxygen in the ratio 1 : 2 : 1