I think the correct answer would be B. Octane is a component of fuel used in internal combustion engines. the dominant intermolecular forces in octane are london dispersion forces. Dipole-dipole bonds happens only with polar substances. Hydrogen bonding occurs when H bonds with an O, F or N atom. Covalent bonds are not intermolecular force rather it is an intramolecular force. Carbon-Hydrogen bonds, as far as I know, are not a type of bond, intermolecular or intramolecular. So, we are left with london dispersion force. It is a temporary force that happens when electrons of two atoms in adjacent would occupy positions that would form dipoles temporarily.
