Which of the following compounds has the maximum enol content?

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

Which of the following orders correctly depicts the decreasing order of stability of carbanion?

Consider the following compounds. Hyperconjugation occurs in:

In the following resonance structures,the curved arrow indicates that electrons are shifted from:

What are the characteristics of the inductive effect?