To determine which of the given compounds has sp² hybridization, we need to understand the structure of each molecule and the hybridization of the central atom in each case.

Option A: CO₂

In carbon dioxide (CO₂), the carbon atom is the central atom. Carbon forms two double bonds with two oxygen atoms.

In this configuration, carbon has two regions of electron density (each double bond counts as one region of electron density). According to the Valence Shell Electron Pair Repulsion (VSEPR) theory, this would result in a linear structure with a bond angle of 180 degrees. The hybridization of the carbon atom, in this case, is sp, because it needs two hybrid orbitals to form the two double bonds.

So, CO₂ does not have sp² hybridization.

Option B: SO₂

In sulfur dioxide (SO₂), the sulfur atom is the central atom. Sulfur forms two double bonds with two oxygen atoms.

However, sulfur also has a lone pair of electrons. This results in three regions of electron density around the sulfur atom (two double bonds and one lone pair). According to the VSEPR theory, this configuration leads to a bent molecular shape.

With three regions of electron density, the hybridization of sulfur is sp². Therefore, SO₂ has sp² hybridization.

Option C: N₂O

In nitrous oxide (N₂O), one nitrogen atom is central. The molecule can be arranged as N=N=O, where the central nitrogen forms a double bond with each of the terminal nitrogen and oxygen atoms.

This gives the central nitrogen two regions of electron density, resulting in linear geometry. The hybridization of the central nitrogen atom here is sp, not sp².

So, N₂O does not have sp² hybridization.

Option D: CO

In carbon monoxide (CO), the carbon atom forms a triple bond with the oxygen atom. This involves one sigma bond and two pi bonds, with one lone pair on each atom.

This gives each atom two regions of electron density, resulting in linear geometry. The hybridization of carbon in CO is also sp.

So, CO does not have sp² hybridization.

Based on the analysis of each option, the correct answer is:

Option B: SO₂