Out of the listed molecules, CO (carbon monoxide) is the nonpolar one.
HF (hydrogen fluoride) are Polar due to the significant electronegativity difference between hydrogen and fluorine, resulting in a bond dipole moment that isn't canceled out by symmetry.
NH₃ (ammonia) is also polar despite having three N-H bonds with bond dipoles. The trigonal pyramidal geometry causes partial cancellation of individual bond dipoles, but a net dipole moment remains due to the lone pair on the nitrogen atom.