The dominant intermolecular force in CH3Cl (chloromethane) is b) dipole-dipole interactions.
CH3Cl is a polar molecule due to the difference in electronegativity between carbon and chlorine. The chlorine atom is more electronegative, which creates a dipole where the chlorine end has a partial negative charge and the carbon end has a partial positive charge. This polarity results in dipole-dipole interactions, where the positive end of one molecule is attracted to the negative end of another. While dispersion forces and hydrogen bonding may play a role, they are not the dominant forces present in this molecule due to its overall polarity.