Arrange the following in decreasing acidic strength.

$$C{H_3} - C{H_2} - CN\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{Ether}^{C{H_3}MgBr}} A\buildrel {{H_3}{O^ + }} \over \longrightarrow B\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{HCl}^{Zn - Hg}} C$$

The correct structure of C is

Glycosidic linkage between C₁ of $$\alpha$$-glucose and C₂ of $$\beta$$-fructose is found in

In base vs. acid titration, at the end point methyl orange is present as