Which one of the following interhalogen compounds has a zero dipole moment?

$\mathrm{IF}{}_7$ is a symmetrical pentagonal bipyramid with no lone pair on I, so all bond dipoles cancel. $\mathrm{ClF}{}_3$ (T-shaped) and $\mathrm{BrF}{}_5$ (square pyramidal) have lone pairs and are polar, and the diatomic $\mathrm{ICl}$ is polar because of unequal electronegativity.