Julie takes a cold glass of clear, colorless liquid out of the refrigerator and puts it on the table. As the liquid warms up to room temperature, Julie sees bubbles of gas form in the liquid and rise to the surface. Which conclusion is best supported by Julie’s observations?

The liquid is a pure substance because it is colorless.
The liquid is a mixture because its temperature rises.
The liquid is a pure substance because it remains liquid when cold.
The liquid is a mixture because it has a gas dissolved in a liquid.