Step 1: Effect of chain length on boiling point.
Boiling point increases with increasing molecular size due to stronger London dispersion forces. Therefore: propan-1-ol (3C) boils lower than butanols (4C), which in turn boil lower than pentan-1-ol (5C).
Step 2: Effect of branching on boiling point.
Among isomers with the same molecular formula, increased branching reduces the contact surface area, weakening van der Waals forces and lowering the boiling point.
Step 3: Compare the two butanols.
Butan-1-ol is straight-chain; butan-2-ol is branched. Therefore butan-2-ol has a lower boiling point than butan-1-ol.
Step 4: Assemble the order.
Combining both factors: propan-1-ol < butan-2-ol < butan-1-ol < pentan-1-ol. This matches option (C).
\[ \boxed{(C)} \]