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.
The pentaacetate of glucose does not react with `H_2N - OH` indicating the absence of

Options

A. `-OH` group
B. `-CHO` group
C. `-COOH` group
D. `-CH_2OH` group