`CH_(3)-underset(" "C_(2)H_(5))underset(|)overset(D)overset(|)(C)-MgBr+CH_(3)-CH_(2)OHrarr`optically active product `'x'`. Here `'x'` is `:`

Explanation

To solve the problem, we need to analyze the reaction between the Grignard reagent and ethanol, and identify the optically active product 'X'.

### Step-by-Step Solution:

1. **Identify the Grignard Reagent**:
The given Grignard reagent is CH₃-C(C₂H₅)-D-MgBr. Here, D represents a deuterium atom (an isotope of hydrogen).

2. **Identify the Alcohol**:
The alcohol involved in the reaction is CH₃-CH₂OH (ethanol).

3. **Understand the Reaction Mechanism**:
Grignard reagents (R-MgX) react with alcohols (R'-OH) through an acid-base reaction. The acidic hydrogen from the alcohol is abstracted by the Grignard reagent, leading to the formation of an alkane and a magnesium alkoxide.

4. **Write the Reaction**:
The reaction can be represented as:
\[ \text{CH}_3-\text{C}(\text{C}_2\text{H}_5)-\text{D}-\text{MgBr} + \text{CH}_3-\text{CH}_2\text{OH} \rightarrow \text{CH}_3-\text{C}(\text{C}_2\text{H}_5)-\text{D}-\text{H} + \text{CH}_3-\text{CH}_2\text{O}^-\text{MgBr} \]

5. **Identify the Products**:
The products of the reaction will be:
- An alkane: CH₃-C(C₂H₅)-D-H (where the MgBr has been replaced by H).
- A magnesium alkoxide: CH₃-CH₂O-MgBr.

6. **Determine the Chirality**:
The product CH₃-C(C₂H₅)-D-H has a chiral center at the carbon atom bonded to C₂H₅, D, and CH₃. This means that the product is optically active.

7. **Conclusion**:
The optically active product 'X' is CH₃-C(C₂H₅)-D-H.

### Final Answer:
The optically active product 'X' is:
\[ \text{CH}_3-\text{C}(\text{C}_2\text{H}_5)-\text{D}-\text{H} \]