At which carbon atom do $\alpha-$ and $\beta-$ glucose differ in the configuration of the $-OH$ group?

Given below are two statements :
Statement $I :$ $D$-glucose pentaacetate does not react with $2,4$-dinitrophenylhydrazine.
Statement $II :$ Starch,on heating with dilute sulfuric acid at $393 \ K$ and $2-3 \ \text{atmosphere}$ pressure,produces glucose.
In the light of the above statements,choose the correct answer from the options given below.

The number of stereoisomers of aldoheptose is $a$ and the number of stereoisomers of ketoheptose is $b$. The ratio of $a/b$ is:

The pair of compounds in which both the compounds give positive test with Tollen's reagent is

Assertion: Glucose and fructose give the same osazone.
Reason: During osazone formation,stereochemistry only at $C_1$ and $C_2$ is destroyed.

Invert sugar refers to an equimolar mixture of: