Synthesis of each molecule of glucose in photosynthesis involves:

The order of stability of the following carbocations :

Compound $$\left( A \right),\,{C_8}{H_9}Br,\,\,\,$$ gives a white precipitate when warmed with alcoholic $$AgN{O_3}.$$ Oxidation of $$(A)$$ gives an acid $$\left( B \right),$$ $${C_8}{H_6}{O_4}.\,\,\left( B \right)$$ easily forms anhydride on heating. Identify the compound $$(A).$$

Arrange the following compounds in order of decreasing acidity :