**Explanation:**

The shape of a molecule can be predicted using the Valence Shell Electron Pair Repulsion (VSEPR) theory. According to this theory, electron pairs (both bonding and non-bonding) around the central atom repel each other and try to get as far away from each other as possible.

In the case of IF4-, the central atom is iodine (I). Let's determine the electron-pair and molecular geometry of IF4- using the VSEPR theory:

**1. Draw the Lewis structure:**
To determine the electron-pair and molecular geometry, we first need to draw the Lewis structure of IF4-.
Iodine (I) is the central atom and it has 7 valence electrons. Fluorine (F) has 7 valence electrons each. Since there are 4 fluorine atoms, the total number of valence electrons in IF4- is:

7 (Iodine) + 4(7) (4 Fluorine) + 1 (extra electron) = 36 valence electrons

To satisfy the octet rule, iodine needs 8 valence electrons. Therefore, it needs 1 more electron, which it gets from the extra electron (-1 charge).

The Lewis structure of IF4- is as follows:

I: 7 valence electrons
F: 7 valence electrons each (4 F atoms)
Extra electron: 1 valence electron

The extra electron forms a lone pair on iodine, and each fluorine atom forms a single bond with iodine.

**2. Determine the electron-pair geometry:**
To determine the electron-pair geometry, we consider both the bonding and non-bonding electron pairs around the central atom. In IF4-, there are 4 bonding pairs (the single bonds between iodine and fluorine) and 1 non-bonding pair (the lone pair on iodine).

The electron-pair geometry is determined by the total number of electron pairs (bonding and non-bonding) around the central atom. In this case, there are 5 electron pairs (4 bonding pairs + 1 non-bonding pair).

**3. Determine the molecular geometry:**
The molecular geometry is determined by the arrangement of the bonding electron pairs around the central atom.

In IF4-, the bonding electron pairs are arranged in a trigonal bipyramidal (TBP) arrangement. This means that the 4 fluorine atoms are arranged in a plane around the central iodine atom, with bond angles of 120°.

However, we also need to consider the lone pair on iodine. The presence of a lone pair causes distortions in the molecular geometry. In this case, the lone pair on iodine occupies one of the equatorial positions, resulting in a see-saw shape. The bond angles between the fluorine atoms and the iodine atom will be less than 120° due to the repulsion from the lone pair.

Therefore, the shape of the IF4- molecule is See-Saw (option b).