Final answer:
Br2 exhibits a nonpolar covalent bond because it consists of two identical bromine atoms that share electrons equally. Other options such as HBr, H2O, and HCl have polar covalent bonds due to differences in electronegativities between hydrogen and the halogens or oxygen.
Step-by-step explanation:
A nonpolar covalent bond is one where the electrons are shared equally between two atoms. This typically occurs between atoms with similar electronegativities. Out of the options provided (HBr, H2O, HCl, Br2), Br2 exhibits a nonpolar covalent bond because it is made of two identical bromine atoms, thereby sharing the electron pair equally.
The bond between hydrogen (H) and carbon (C), as in the case of methane (CH4), is also a nonpolar covalent bond. Although carbon and hydrogen do not have identical electronegativities, they are similar enough that the bonding electrons are shared relatively equally.