(a)
Boiling point $\propto$ molecualr mass $\propto \frac{1}{branching}$
$(\therefore$ surface area decreases)
$\therefore$ $n$-hexane has the highest boiling point among the given.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.