Rocks are made up deposited minerals that form and condense into rocks
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When temperature of liquid is increased, liquid gets thinner and thinner and hence it's viscosity decreases.
Density = mass/volume.
As we increase the temperature, volume of the liquid starts to increase but mass of the liquid remains constant. As a result, density of liquid decreases.
Hope this helps!
B, radon is correct. Interestingly, it often collects in basements from radioactive decay of rocks such as granite that contain uranium. Because it is an unreactive noble gas and because it is denser than air it sits in basements and must be pumped out. It collects in human lungs and is the second leading cause of lung cancer behind smoking.