Which of the following is the most correct electron displacement for a nucleophilic reaction to take place?

State True or False for the following statements regarding the $-NO_2$ group in nitrobenzene:
$(i)$ In resonance,it acts as an electron-donating group,and in the inductive effect,it acts as an electron-attracting group.
$(ii)$ It acts as an electron-donating group in both resonance and the inductive effect.
$(iii)$ It acts as an electron-attracting group in both resonance and the inductive effect.
$(iv)$ It acts as an electron-attracting group in resonance and an electron-donating group in the inductive effect.

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

The correct order of the electron-donating or withdrawing effect (inductive/mesomeric effect) for the groups $-NH_2, -OCH_3, -C_6H_5$,and $-NO_2$ is:

The migratory aptitude of the following groups in decreasing order is:

Explain the factors affecting the extent of inductive effect.