Which of the following has the highest boiling point?

All alkyl halide has the same molecular formula, so the trend of boiling point depends on the surface area of each molecule.

As branching in a molecule increases, surface area decreases and thereby the van Der Waal forces also decreases because molecule attains spherical shape with less surface area. So, the molecule that has the lowest branching has the maximum boiling point.

Hence, the correct option is A.