Answer:
(A) BeCl2
Explanation:
At room temperature Berium Chloride, BeCl2, is a solid as it forms a coordinate covalent bond between Berium, Be and Chlorine, Cl
While in the gaseous state, it is a single molecule with higher affinity for other BeCl2 molecules due to the potential of existing intramolecular forces between BeCl2 molecules due to its electron deficiency within each molecule