Answer: Covalent
Step-by-step explanation: A covalent bond is formed by sharing of electrons and usually present in non metals whereas ionic bond is formed by transfer of electrons and is formed by metals and non metals.
A metallic bond is present in metals which is formed due to the presence of valence electrons
A neutral bond is one which there is no formation of charges. Both covalent and ionic bonds result into formation of neutral compounds.
Thus A and B forms a covalent bond as there is sharing of electrons between them.