Carbohydrates are polyhydroxy aldehydes or ketones and are also called saccharides. Glucose is an example of monosaccharides. Glucose `(C_6H_12O_6)` is an aldohexose and its open chain structure was assigned on the basis of many reactions as evidences like presence of carbonyl group, presence of straight chain, presence of five-OH groups, etc. Glucose is correctly named as D(+)Glucose. Glucose is found to exist in two different crystalline forms which are named as `alpha` and `beta`. Despite having the aldehyde group, glucose does not give 2,4-DNP test.
Glucose on oxidation with `HNO_3` gives a dicarboxylic acid called saccharic acid. This result validates the fact that Glucose possesses :

Options

A. `-CHO` group
B. `-OH` group
C. a straight chain
D. both `- CHO and -CH_2OH` groups at the terminals of the chain