The bubbles indicate that there is a gas dissolved in the liquid, which may remain dissolved when the liquid is very cold, inside the refrigerator.
When the temperature of the liquid increases, it reduces its ability to dissolve the gas and the gas escapes (bubbles) from the liquid.
At the end, the behavior of the liquid permits you to conclude that the liquid is a mixture because it has a gas dissolved in it.
The presence of ozone in the troposphere has been considered as pollutant. Thus, option A is correct.
The atmosphere has been divided into five layers based on the availability and the composition of different elements.
<h3>Troposphere</h3>
The troposphere has been the lowest layer of the atmosphere. It has been closed to the earth surface and provides with clouds and maintain weather.
The gases on the troposphere are used by the organisms for living purpose. The ozone has been a harmful gas for living organisms.
Thus, the presence of ozone in the troposphere has been considered as pollutant. Thus, option A is correct.
Learn more about troposphere, here:
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