Understand Statement I

In nitration of benzene, the electrophile is the nitronium ion, $\ce{NO2+}$, generated from concentrated $\ce{HNO3}$ and $\ce{H2SO4}$.

The key electrophilic substitution step is: $\ce{C6H6 + NO2+ -> [sigma\ complex] -> C6H5NO2}$

Thus, nitration of benzene indeed involves attack of benzene on an electrophile followed by formation of the arenium ion (sigma complex) and deprotonation.

Therefore, Statement I is correct.

Understand Statement II

Electrophilic substitution of benzene is promoted by generation of a stronger electrophile, which is usually done using a Lewis acid such as $\ce{AlCl3}$, $\ce{FeCl3}$, etc.

Examples:

• Halogenation: $\ce{Cl2/FeCl3}$
• Friedel–Crafts: $\ce{RCl/AlCl3}$

A Lewis base donates electron pair and would not promote electrophilic substitution in the usual mechanism.

Therefore, Statement II is incorrect.

Evaluate options

• A: Both incorrect $\rightarrow$ false
• B: Statement I correct, Statement II incorrect $\rightarrow$ true
• C: Statement I incorrect, Statement II correct $\rightarrow$ false
• D: Both correct $\rightarrow$ false

Final answer

The correct option is B.