To understand which atomic orbitals form a square planar complex, we need to consider the geometry and hybridization of the complex.

Geometry of Square Planar Complex:
A square planar complex consists of a central metal atom surrounded by four ligands arranged in a square plane. The ligands are positioned at the corners of the square, and the metal atom is in the center.

Hybridization in Square Planar Complex:
To form a square planar complex, the central metal atom undergoes hybridization to form a set of hybrid orbitals. These hybrid orbitals will then overlap with the ligand orbitals to form the coordination bonds.

The square planar geometry is achieved through the hybridization of the central metal atom's atomic orbitals. In this case, the central metal atom should have a coordination number of 4.

Hybridization of Atomic Orbitals:
The atomic orbitals involved in the hybridization of the central metal atom in a square planar complex are:

1. s orbital: The s orbital is always involved in hybridization and contributes one of the hybrid orbitals. It forms a part of the hybrid set.

2. px and py orbitals: Both the px and py orbitals are involved in hybridization and contribute two of the hybrid orbitals. They form a part of the hybrid set.

3. dx2-y2 orbital: The dx2-y2 orbital is involved in hybridization and contributes one of the hybrid orbitals. It forms a part of the hybrid set.

Therefore, the correct option is B - s, px, py, dx2-y2. These atomic orbitals form the hybrid set in a square planar complex, allowing the central metal atom to achieve a square planar geometry.

In summary, a square planar complex is formed through the hybridization of s, px, py, and dx2-y2 atomic orbitals. These hybrid orbitals then overlap with the ligand orbitals to form the coordination bonds.