It could be argued against our claim for the equivalence between MMBs and EDMBs that linear EDMBs are rare in molecules, whereas linear 3c-4e ERMBs, such as those of Fig. , are common in molecules . In this regard it must be emphasized that there are two types of 3c-2e bonds: supported and unsupported 3c-2e bonds . The EDMBs of H3 + and B2H6 are of supported type and tend to be bent; however, the EDMBs in PCMs and the Ah and Ai phases of group-15 and -16 elements are of unsupported type, such as the B-H-B and Al-H-Al bonds in B2H7 ꟷ and Al2H7 ꟷ . It has been proposed that these unsupported bonds can be either bent or linear; bent in the absence of a crystal lattice and linear when the crystal lattice is present . Therefore, the existence of linear unsupported EDMBs in crystalline solids is justified due to the presence of the translational symmetry of the crystal lattice. These reasonings allow us to tentatively propose that MMBs with the geometries of Fig. are likely the typical EDMBs in solids.