Vanillin `A[C_8H_8O_3]` is isolated from vanilla beans. It gives intense blue colour with neutral `FeCl_3` and also gives+ve Tollen's test. It reacts with conc. HBr to give a compound B. One mole of vanillin gave one mole of AgI with Zeise's active methoxy estimations. Compound B on oxidation with Tollen's reagent gave a catechol derivative. Compound B can be prepared from catechol by Gattermann Koch reaction.
Compound B on heating with zinc dust will give

Options

A.
B.
C.
D.

Answer

C