Analyze Statement (I): $\mathrm{S_N2}$ reactions are stereospecific

In an $\mathrm{S_N2}$ reaction, the nucleophile attacks the carbon atom from the backside of the leaving group.

This causes Walden inversion at the chiral center.

So, if the substrate is optically active and has a chiral center, the configuration changes in a definite way: $R \to S \quad \text{or} \quad S \to R$ (depending on priority order after substitution).

Thus, the reaction is stereospecific because a given stereoisomeric reactant gives a specific stereoisomeric product.

Therefore, Statement (I) is true.

Analyze Statement (II): $\mathrm{S_N1}$ reactions generally give racemic mixtures

In an $\mathrm{S_N1}$ reaction, the leaving group first departs to form a planar carbocation intermediate.

Since the carbocation is planar, the nucleophile can attack from either side:

• front side attack
• back side attack

Hence, both enantiomers are formed, and the product is generally a racemic mixture (though often not perfectly 50:50 due to ion-pair effects, but generally racemization is observed).

Therefore, Statement (II) is true.

Choose the correct option

Since both statements are true, the correct option is: $\boxed{D}$

Comparison with stored answer

Stored correct answer: $D$

My derived answer also is $D$, so they agree.