The species having pyramidal shape is

The correct option is OSF₂.

To determine the molecular shape of ${\mathrm{OSF}}_2$ (thionyl fluoride) and understand why it is pyramidal, we can use the Valence Shell Electron Pair Repulsion (VSEPR) theory. Let's analyze the central atom and its bonding:

1. Central Atom and Valence Electrons:
In thionyl fluoride (${\mathrm{OSF}}_2$), sulfur (S) is the central atom. Sulfur belongs to Group 16 of the periodic table and has 6 valence electrons.

2. Bonding and Electron Sharing:
- The oxygen (O) atom forms a double bond with sulfur (sharing 2 electrons).
- Each of the two fluorine (F) atoms forms a single bond with sulfur (sharing 1 electron per fluorine atom, total 2 electrons).
- Therefore, sulfur uses 4 of its valence electrons to form bonds: 2 for the $S=O$ double bond and 2 for the two $S-F$ single bonds.

3. Determining Lone Pairs:
The number of remaining non-bonding valence electrons on the sulfur atom is:
$6-4=2\text{electrons}$.
These 2 remaining valence electrons constitute 1 lone pair on the sulfur atom.

4. Steric Number and Molecular Geometry:
Under VSEPR theory, double bonds and single bonds each count as one active bonding region (or electron group) around the central atom. The steric number (SN) is the sum of the number of bonded atoms and the number of lone pairs on the central atom:
- Number of bonded atoms (1 oxygen + 2 fluorines) = 3
- Number of lone pairs = 1
- Steric Number = $3+1=4$.

A steric number of 4 corresponds to a tetrahedral electron-pair geometry. However, because there is 1 lone pair and 3 bonding groups, the lone pair occupies one of the tetrahedral positions. The repulsion from this lone pair pushes the three bonding pairs downward, resulting in a pyramidal (trigonal pyramidal) molecular shape.

Why other options do not have a pyramidal shape:
- ${\mathrm{SO}}_3$ (Sulfur trioxide): Sulfur has 6 valence electrons, all used in bonding with three oxygen atoms (three double bonds) with 0 lone pairs. Steric number is 3, giving a trigonal planar shape.
- ${\mathrm{BrF}}_3$ (Bromine trifluoride): Bromine has 7 valence electrons. It forms three single bonds with fluorine, leaving 4 non-bonding electrons (2 lone pairs). With SN = 5 (3 bonding pairs + 2 lone pairs), it has a T-shaped geometry.
- ${\mathrm{SiO}}_3^{2-}$ (Silicate ion): Silicon has 4 valence electrons + 2 from the negative charge = 6 electrons, which form bonds with three oxygen atoms with 0 lone pairs on silicon. This results in a trigonal planar geometry.