A chemist concludes that sample Z is ionic after measuring its high melting point and its ability to conduct electricity only when molten. Which additional macroscopic observation would most strongly reinforce this conclusion?
a) Z can be hammered into thin sheets without cracking.
b) Z cleaves cleanly along flat planes when struck.
c) Z dissolves readily in a nonpolar solvent such as hexane.
d) Z conducts electricity well in the solid state.