Assertion:- Styrene on reaction with HBr gives 1-Bromo-1-Phenyl ethane
Reason:- Benzyl carbocation is more stable than alkyl carbocation 

Correct Answer: Option (a)

Styrene reacts with HBr to give 1-Bromo-1-phenyl ethane. 
That is TRUE.

Styrene is C₆H₅–CH=CH₂ (a phenyl group attached to an ethene unit).

When HBr adds to an alkene, it follows Markovnikov's rule:

H⁺ adds to the carbon with more hydrogens, and Br⁻ goes to the carbon with fewer hydrogens.

In styrene:

CH=CH₂: The double bond is between a CH (next to the phenyl) and CH₂.

So H⁺ adds to the CH₂ (less substituted carbon).

This leaves a carbocation at the benzylic position (C⁺ next to the phenyl group), which is very stable due to resonance with the aromatic ring.

The resulting product is:
C₆H₅–C(Br)H–CH₃ → 1-Bromo-1-phenyl ethane

So the assertion is true 

Reason:

Benzyl carbocation is more stable than an alkyl carbocation. 
That is also TRUE.

A benzyl carbocation (C₆H₅–CH₂⁺) is highly stabilized by resonance with the phenyl ring.

In contrast, a regular alkyl carbocation lacks such delocalization.

So the reason is also true.

Is the reason the correct explanation?

Yes. The product formation (1-Bromo-1-phenyl ethane) is due to the formation of a benzyl carbocation, which is highly stable. This drives the reaction to form that specific product.

So the reason directly explains the assertion.

Final Answer: (a)

Both Assertion & Reason are correct, and Reason is the correct explanation of Assertion.