Part a what is the predominant intermolecular force in the liquid state of each of these compounds: ammonia (nh3), carbon tetrabromide (cbr4), and dichloromethane (ch2cl2)?

The predominant inter-molecular forces in the compounds are as follows:
ammonia - hydrogen bond.
carbon tetrabromide - dispersion forces.
dichloro methane - dipole - dipole forces.
Dipole -dipole forces usually predominates in polar compounds and hydrogen bond predominates in compounds that have OH, NH OR HF.