The following effect is known as . . . . . .

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 $IV > V > I > II > III$.

How many compounds among the following compounds show inductive,mesomeric as well as hyperconjugation effects?

The correct order for the rate of decarboxylation of the following compounds with sodalime will be:

Identify the compound which has the maximum number of no-bond resonance (hyperconjugation) structures.

The $-NO_2$ group in the following conjugated system shows: