The right answer is carbohydrates.
Carbohydrates (Cn(H2O)m) are a set of substances whose basic units are the simple sugars called oses or monosaccharides.
Carbohydrates have been defined as polyhydroxy aldehydes or ketones. They are water-soluble and reducing compounds.
Carbohydrates are present throughout the biosphere and represent by weight the predominant class among organic molecules. Most of the carbohydrate collected comes from photosynthesis, a process that incorporates CO2 into carbohydrates.