Final answer:
The bond strengths for phosphorous-halogen bonds are ranked by considering bond dissociation energy and electronegativity; the correct order from weakest to strongest is PI < PBr < PF.
Step-by-step explanation:
The strength of the bonds involving phosphorous and different halogens - bromine (Br), fluorine (F), and iodine (I) - can be determined by considering factors such as bond dissociation energy and the electronegativity of the halogens. The bond dissociation energy generally decreases in the order F > Cl > Br > I, which indicates the relative strength of the bonds, making C-F the strongest due to fluorine's high electronegativity and smaller size, which allows for a greater overlap of orbitals and thus a stronger bond.
The correct order starting from the weakest bond to the strongest bond is: pi < pbr < pf, which corresponds to option (a).