There are two important factors that you need to consider concurrently when judging the melting/boiling points of molecules:

Typically, when comparing intermolecular forces among various molecules, the differences need to be significant. For example, in terms of bond strength, the order might be CaCl2 > H2O > CF3 > CH4, where ionic bonds (intramolecular) > hydrogen bonding > dipole-dipole forces > London dispersion forces (LDF). However, when intermolecular forces are relatively similar with low polarity, the key factor becomes molecular weight—the larger the molecule, the higher the melting or boiling point. Therefore, in a case like CBr4 > CHBr3 > CH3Br, the stark difference in molecular weight determines the melting and boiling points.

It's not always about prioritizing molecular weight over polarity; the approach can vary based on the specific question and the factors influencing the melting/boiling point. If molecular weights differ greatly, like in your question, molecular weight becomes the primary factor. Conversely, when molecular weights are similar, intermolecular forces and polarity play a more significant role in distinguishing between molecules.

Essentially, the reason why CBr4 has the highest melting/boiling point among these examples is due to its greater molecular weight. Larger molecules generally have more bonds, requiring more energy to break them. This translates into higher melting and boiling points. The Dental Admission Test (DAT) tends to focus on questions that standardize these concepts, emphasizing intermolecular forces' impact on molecular properties. However, questions related to molecular weight can also appear on the exam.

The melting point will increase as the branching increases since this would make the molecule more compact and sphere-like (when comparing the branched molecules). So to recap, branching will decrease the melting point when considering linear molecules, however, it will increase the melting point when considering the branched molecules.

As branching increases, the boiling point decreases.

As branching decreases, the boiling point increases.