Final answer:
Compound B is mostly held together by metallic bonds.
Step-by-step explanation:
Compound B is mostly held together by metallic bonds.
Metallic compounds are held together by a sea of delocalized electrons that are shared among the metal atoms. This sea of electrons allows metals to conduct electricity and heat well, and gives them their characteristic properties of malleability and ductility. Compound B, with its much higher boiling point compared to Compound A, indicates a stronger metallic bond.