The correct answer to this question is B, square planar. While IF4- has an octahedral electron geometry, the molecular geometry of IF4- takes on a square planar shape. The cause of this is that iodine carries two lone pairs, with one above the plane on the x-axis and one below the plane on the x-axis.
Due to their negative charges repeling against one another, these lone pairs occupy opposite electron domains, canceling out when acting upon the fluorines and, thus, creating the square planar shape. THe fluorine molecules surround it at right angles to each other, approximately bonding at 90 degrees.