David observed properties of four different compounds, only one of which is an ionic

David observed properties of four different compounds, only one of which is an ionic compound. His observations are shown in the chart. A 2-column table with 4 rows. The first column labeled compound has entries W, X, Y, Z. The second column labeled observations has entries is a hard solid, melts at 44 degrees C, has a molecular structure; is a brittle solid, does not conduct electricity in water, has a crystal structure; is a hard solid, conducts electricity, has a molecular structure; is a brittle solid, melts at 801 degrees C, has a crystal structure. Which is most likely the ionic compound? W X