The hydrocarbon with highest boiling point is
(a) hexane
Explanation for the correct options: The boiling point of hydrocarbon depends upon the length of the carbon chain. An increase in the number of carbon also increases the boiling point of the hydrocarbon. Hexane contains six carbon atoms in the chain and therefore, option (a) is the correct answer.
Explanation for the incorrect options:
Option (b) The boiling point depends on the number of the carbon chains. Pentane contains five carbons in the chain and therefore, it's not the correct answer.
Option (c): The boiling point depends on the number of the carbon chains. Butane contains four carbons in the chain and therefore, it's not the correct answer.
Option (d): The boiling point depends on the number of the carbon chain. Propane contains three carbons in the chains and therefore, it's not the correct answer.