Identify the correct order of reactivity for the following pairs towards the respective mechanism

(A)

(B)

(C) Electrophilic substitution

(D) Nucleophilic substitution

Choose the correct answer from the options given below:

Rule: The rate of an SN2 reaction decreases as the steric hindrance around the leaving group increases:
Primary 1 > Secondary 2>Tertiary 3 degree
hence a is correct.

For SN1 reaction, The rate of an  reaction depends directly on the stability of the carbocation intermediate formed during the rate-determining step, Benzylic=Allylic > Tertiary > Secondary > Primary
hence B is correct

Electrophilic Aromatic Substitution (EAS)

• Rule: Electron-donating groups (EDGs) activate the aromatic ring and increase the reaction rate, while electron-withdrawing groups (EWGs) deactivate the ring and decrease the reaction rate
  Chlorobenzene >1-chloro-4-nitrobenzene
  hence C is correct
  Nucleophilic Aromatic Substitution
  The presence of strong electron-withdrawing groups (-NO2) at the ortho or para positions relative to the leaving group stabilizes the intermediate Meisenheimer complex via resonance, significantly boosting reactivity.
  hence d correct