In a pure sample of carbon monoxide (CO), the primary intermolecular force present is the dipole-dipole interaction. This occurs because carbon monoxide is a polar molecule. The carbon (C) atom has a partial positive charge, while the oxygen (O) atom has a partial negative charge.
Due to this polarity, the molecules are attracted to each other, with the positive end of one CO molecule facing the negative end of another. Additionally, there are also London dispersion forces present, but these are relatively weak compared to the dipole-dipole interactions. In summary, the most significant intermolecular force in a pure sample of CO is the dipole-dipole interaction, supplemented by weaker London dispersion forces.