A wax sample is heated. Melting starts at $45^\circ \text{C}$ and is complete at $49^\circ \text{C}$. A liquid sample is heated. Boiling starts at $141^\circ \text{C}$ and the temperature stays at $141^\circ \text{C}$ during boiling. Which conclusion can be drawn from these observations?
- ABoth substances are impure.
- BBoth substances are pure.
- CThe wax is not a pure substance and the liquid is a pure substance.
- DThe wax is a pure substance and the liquid is not a pure substance.