Electrically, what does a crystal look like?

Electrically, a quartz crystal acts as an extremely high-Q tuned circuit. Its equivalent circuit consists of a series combination of inductance, capacitance, and resistance, all shunted by another parallel capacitance representing the electrodes and mounting hardware. The Quality Factor (Q) of a crystal can easily exceed 10,000, and sometimes reaches into the millions. This is vastly superior to a standard inductor-capacitor (LC) tuned circuit, which typically has a Q of a few hundred at best. Because of this very high Q, crystals are highly stable and exhibit an extremely narrow bandwidth. They are not meant to be highly 'variable' or 'low Q', which easily rules out the incorrect options.