Which group from the following is responsible for the $(-R)$ effect?

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 represents an incorrect electromeric effect?

Given below are two statements:
Statement $I$: In $O_2N-C_6H_4-CH^+-C_6H_4-OCH_3$,the carbocation is stabilised by $+R$ effect of $-OCH_3$ group.
Statement $II$: In $O_2N-C_6H_4-CH^--C_6H_4-OCH_3$,the carbanion is stabilised by $-R$ effect of $-NO_2$ group.
In the light of the above statements,choose the correct answer from the options given below:

The functional group that shows negative resonance effect ($-R$ effect) is:

Negative inductive effect ($-I$ effect) is shown by: