Molecular symmetry determines zero dipole moment

Steps:

• Identify molecular geometry for each option using VSEPR theory.
• Assess symmetry: symmetrical shapes cancel bond polarities, resulting in zero net dipole.
• Evaluate BF3: trigonal planar, highly symmetric.
• Evaluate others: check if symmetry leads to zero dipole or not.

Why A is correct:

• Boron trifluoride (BF3) has trigonal planar geometry with identical B-F bonds, symmetrically arranged to cancel dipole moments (vector sum = 0).

Why the others are wrong:

• B: Methane (CH4) is tetrahedral and symmetric, so it also has zero dipole moment.
• C: Phosphorus pentafluoride (PF5) is trigonal bipyramidal and symmetric, so it also has zero dipole moment.
• D: Not enough information (option incomplete).

Final answer: Not enough information.