At stp, fluorine is a gas and bromine is a liquid because, compared to fluorine, bromine has
(1) stronger covalent bonds
(2) stronger intermolecular forces
(3) weaker covalent bonds
(4) weaker intermolecular forces

The physical state of a substance (solid, liquid or gas) is dependent on the forces keeping the molecules of the substance together, known as intermolecular forces. The stronger the intermolecular forces, the closer the molecules will be and they would tend towards solid behavior. Weaker intermolecular forces mean more gas-like behavior. Therefore, the answer is (2), bromine has stronger intermolecular forces.