Here's why:

* Lewis Structure: The Lewis structure of CO shows a triple bond between the carbon and oxygen atoms. This triple bond consists of one sigma bond and two pi bonds.

* Hybridization: The carbon atom in CO undergoes sp hybridization, meaning it has two hybrid orbitals. These hybrid orbitals point in opposite directions, resulting in a linear geometry.

* Electron Domains: There are two electron domains around the carbon atom (the triple bond with oxygen), and two electron domains around the oxygen atom (the triple bond with carbon and two lone pairs). This also supports the linear shape.

Therefore, CO has a linear molecular shape with the carbon and oxygen atoms aligned in a straight line.