**SN2 Reaction at an Asymmetric Carbon Atom of a Dextro Alkyl Halide**

When an SN2 (substitution nucleophilic bimolecular) reaction occurs at an asymmetric carbon atom of a dextro alkyl halide, it typically gives a laevo (levorotatory) product. Let's understand why this is the case.

**SN2 Reaction**

SN2 reactions are a type of nucleophilic substitution reactions that involve the simultaneous attack of a nucleophile on the carbon atom bearing the leaving group. In SN2 reactions, the stereochemistry of the starting material is inverted, meaning the product is the mirror image (enantiomer) of the starting material.

**Asymmetric Carbon Atom**

An asymmetric carbon atom, also known as a chiral carbon atom, is a carbon atom bonded to four different groups or atoms. This carbon atom is non-superimposable on its mirror image, resulting in the existence of two enantiomers. Enantiomers are molecules that are mirror images of each other and cannot be superimposed.

**Dextro Alkyl Halide**

A dextro alkyl halide is an alkyl halide that exhibits dextrorotation or rotates plane-polarized light to the right. This indicates that the compound is optically active and the molecule itself is chiral.

**SN2 Reaction Outcome**

When an SN2 reaction occurs at an asymmetric carbon atom of a dextro alkyl halide, the stereochemistry of the product is determined by the inversion of configuration at the reaction center. This means that the product will be the enantiomer with opposite configuration compared to the starting material.

Since the starting material is dextro (rotates plane-polarized light to the right), the product, which is the enantiomer of the starting material, will be laevo (rotates plane-polarized light to the left). This is because the inversion of configuration results in the opposite rotation of plane-polarized light.

Therefore, the correct answer is option 'a) Laevo product' since an SN2 reaction at an asymmetric carbon atom of a dextro alkyl halide always gives a laevo product.

It's important to note that this is a general trend and may not hold true for all specific cases. The actual outcome of an SN2 reaction can be influenced by various factors such as steric hindrance, solvent effects, and the nature of the nucleophile and leaving group.