Understand that a molecule is IR-active if it has a changing dipole moment during its vibration. This means the molecule must be polar or have a vibration that changes its dipole moment.
Recall that homonuclear diatomic molecules like N\_2, O\_2, and Cl\_2 consist of two identical atoms, so they have no permanent dipole moment and their vibrations do not produce a change in dipole moment.
Recognize that CO is a heteronuclear diatomic molecule composed of two different atoms (carbon and oxygen), which creates a permanent dipole moment.
Since CO has a permanent dipole moment, its vibrational modes cause a change in dipole moment, making it IR-active.
Therefore, among the given molecules, only CO will absorb infrared radiation and be IR-active.