Formic acid is a stronger acid than acetic acid. This can be explained using

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

Among the following,the most acidic compound is

Which of the following has the strongest $+I$ effect?

What is the correct order of acidity of the protons marked $H_A, H_B, H_C,$ and $H_D$ in the given compound?

The higher stabilities of $tert$-butyl cation over isopropyl cation and $trans-2-butene$ over propene,respectively,are due to orbital interactions involving