With respect to the compounds I-V, choose the correct statement(s).

A

The acidity of compound I is due to delocalization in the conjugate base.

B

The conjugate base of compound IV is aromatic.

C

Compound II becomes more acidic, when it has a $$-NO_{2}$$ substituent.

D

The acidity of compounds follows the order I > IV > V > II > III.