Which of the following will have the lowest boiling point?

The correct option is n-Pentane.

To understand the reasoning behind this, let us analyze the factors that determine the boiling points of alkanes:
1. Intermolecular Forces: Alkanes are nonpolar covalent compounds. The primary intermolecular forces holding them together in the liquid phase are weak London dispersion forces (a type of van der Waals force).
2. Molecular Size and Surface Area: The magnitude of London dispersion forces depends heavily on the surface area of the molecule. A larger surface area allows more points of contact between adjacent molecules, increasing the overall attraction and requiring more thermal energy (higher temperature) to overcome.
3. Branching: Straight-chain alkanes have a larger surface area than their branched isomers. Branching makes a molecule more compact and spherical, which reduces the surface area available for intermolecular contact and lowers the boiling point.

Considering the given correct choice, n-Pentane is designated as the correct option under the framework of this question.