Explanation:

Permanent dipole moment arises due to the presence of polar bonds in a molecule. A polar bond is formed when two atoms of different electronegativity are bonded together. Due to the difference in electronegativity, the electron density in the bond shifts towards the more electronegative atom, making it partially negative and the other atom partially positive. The magnitude of the dipole moment depends on the electronegativity difference and the bond length.

Let's analyze the given molecules:

a) SiF4 - Silicon tetrafluoride has a tetrahedral geometry with four polar Si-F bonds. However, the dipole moments of these bonds cancel out each other due to the symmetry of the molecule. Hence, SiF4 has no net dipole moment.

b) XeF4 - Xenon tetrafluoride has a square planar geometry with four polar Xe-F bonds. Similar to SiF4, the dipole moments of these bonds cancel out each other due to the symmetry of the molecule. Hence, XeF4 has no net dipole moment.

c) SF4 - Sulfur tetrafluoride has a trigonal bipyramidal geometry with four polar S-F bonds and one lone pair of electrons on sulfur. The lone pair creates an asymmetric distribution of electron density and breaks the symmetry of the molecule, resulting in a net dipole moment.

d) BF3 - Boron trifluoride has a trigonal planar geometry with three polar B-F bonds. However, the molecule is symmetrical and the dipole moments of the bonds cancel out each other, resulting in no net dipole moment.

Hence, the correct answer is option 'C' SF4.