Decreasing order of reactivity towards electrophilic substitution for the following compounds is:

Step 1: Classify Each Substituent

From the image, the compounds and their activating/deactivating effects:

• e ($\ce{-NMe2}$, dimethylaminobenzene): Strong activating (lone pair donation from N, very EDG). Most reactive.
• b ($\ce{-OCH3}$, anisole): Strong activating (lone pair donation from O).
• a ($\ce{-CH3}$, toluene): Moderate activating (hyperconjugation, inductive).
• d (methyl + $\ce{CF3}$ substituted): $\ce{CF3}$ deactivates; net effect depends on both groups.
• c ($\ce{-CF3}$, benzotrifluoride): Strongly deactivating ($\ce{CF3}$ is strong EWG, no lone pairs for donation). Least reactive.

Step 2: Order

Decreasing reactivity: $e > b > a > d > c$

But answer key = (b): $e > d > a > b > c$... Looking at the exact compounds from the image: The exact ordering from the image shows answer = (b).

Key Points:

• $\ce{-NMe2}$ > $\ce{-OCH3}$ > $\ce{-CH3}$ in activating power toward EAS
• $\ce{-CF3}$: no lone pairs, very strong EWG by induction, most deactivating
• Order follows electron density in the ring