Final answer:
IBr contains a polar covalent bond because the electronegativity difference between iodine and bromine is present but not large enough to form an ionic bond.
Step-by-step explanation:
The question asks which of the given compounds contains a polar covalent bond. A polar covalent bond is characterized by the unequal sharing of electrons between atoms, which occurs when there is a significant electronegativity difference between the atoms but not great enough to result in an ionic bond. In compounds such as NaCl, SrF2, and KCl, the difference in electronegativity between the metal cations (Na+, Sr2+, K+) and the nonmetal anions (Cl−, F−) is considerable, leading to the formation of ionic bonds. However, in the case of IBr, the electronegativity difference between iodine and bromine is not as significant, leading to the formation of a polar covalent bond. Therefore, the correct answer is E. IBr.