(a)
Solubility of alcohols in water decreases as the size of alkyl group increases because tendency to form hydrogen bonding decreases. So, the order of solubility is as
Ethanol > $n$-propanol > $n$-butyl alcohol
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.