Step 1: Concept
This is a competition between Williamson Ether Synthesis ($S_N2$) and Elimination ($E2$).
Step 2: Meaning
Sodium ethoxide is a strong base and a strong nucleophile. Isopropyl chloride is a secondary ($2^\circ$) alkyl halide.
Step 3: Analysis
When a secondary alkyl halide reacts with a strong, hindered base like ethoxide, elimination ($E2$) becomes the dominant pathway over substitution. The $\text{H}$ from the $\beta$-carbon and the $\text{Cl}$ are removed to form a double bond.
$\text{CH}_3\text{CH}(\text{Cl})\text{CH}_3 + \text{NaOCH}_2\text{CH}_3 \rightarrow \text{CH}_3\text{CH}=\text{CH}_2$ (Propene) + $\text{CH}_3\text{CH}_2\text{OH}$ + $\text{NaCl}$.
Step 4: Conclusion
The major product X is propene.
Final Answer: (C)