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Read the passage given below and answer the following questions:
Carbohydrates are polyhydroxy aldehydes and ketones and those compounds which on hydrolysis give such compounds are also carbohydrates. The carbohydrates which are not hydrolysed are called monosaccharides. Monosaccharides with aldehydic group are called aldose and those which free ketonic groups are called ketose. Carbohydrates are optically active. Number of optical isomers $= 2^n$
Where $n =$ numberofasymmetric carbons. Carbohydrates are mainlysynthesised by plants during photosynthesis. The monosaccharides give the characteristic reactions of alcohols and carbonyl group (aldehydes and ketones). It has been found that these monosaccharides exist in the form of cyclic structures. In cyctization, the $-OH$ groups $($generally $C_5$ or $C_4$ in aldohexoses and $C_5$ or $C_6$ in ketohexoses$)$ combine with the aldehyde or keto group. As a result, cyclic structures of five or six membered rings containing one oxygen atom are formed, e.g., glucose forms a ring structure. Glucose contains one aldehyde group, one $IO$ alcoholic group and four $2^\circ$ alcoholic groups in its open chain structure.
The following questions are multiple choice questions. Choose the most appropriate answer:

1. First member of ketos sugar is:

1. Ketotriose.
2. Ketotetrose.
3. Ketopentose.
4. Ketohexose.

2. In $CH_2OHCHOHCHOHCHOHCHOHCHO$, the number of optical isomers will be:

1. $16$
2. $8$
3. $32$
4. $4$

3. Some statements are given below:

1. Glucose is aldohexose.
2. Naturally occurring glucose is dextrorotatory.
3. Glucose contains three chiral centres.
4. Glucose contains one $1^\circ$ alcoholic group and four $2^\circ$ alcoholic groups.

Among the above, correct statements are:

1. $1$ and $2$ only
2. $3$ and $4$ only
3. $1, 2$ and $4$ only
4. $1, 2, 3$ and $4$

4. Two hexoses fonn the same osazone, find the correct statement about these hexoses.

1. Both of them must be aldoses.
2. They are epimers at $C-3.$
3. The carbon atoms $I$ and $2$ in both have the same configuration.
4. The carbon atoms $3, 4$ and $5$ in both have the same configuration.

5. Which of the following reactions of glucose can be explained only by its cyclic structure?

1. Glucose forms cyanohydrin with HCN.
2. Glucose reacts with hydroxylamine to form an oxime.
3. Pentaacetate of glucose does not react with hydroxylamine.
4. Glucose is oxidised by nitric acid to gluconic acid.