Step 1: Understanding the Concept
Alcoholic \(\text{KOH}\) brings about \(\beta\)-elimination (dehydrohalogenation) of haloalkanes.
Step 2: Locate the groups
In 1-chlorobutane, \(\text{CH}_{3}\text{CH}_{2}\text{CH}_{2}\text{CH}_{2}\text{Cl}\), chlorine is on \(\text{C-1}\) and the only \(\beta\)-hydrogens are on \(\text{C-2}\).
Step 3: Elimination
Removing \(\text{HCl}\) forms a double bond between \(\text{C-1}\) and \(\text{C-2}\).
\(\text{CH}_{3}\text{CH}_{2}\text{CH}_{2}\text{CH}_{2}\text{Cl}\rightarrow \text{CH}_{3}\text{CH}_{2}\text{CH}=\text{CH}_{2}\)
Final Answer:
The product is but-1-ene.
\[ \boxed{\text{(D) }\text{But-1-ene}} \]