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 Y Z