Subsets of {dog, cat, fish} are Ф, {dog}, {cat}, {fish}, {dog, cat}, {dog, fish}, {cat, fish}, {dog, cat, fish}.
natural selection light water and carbon dioxide
Layer 8 is older than layer 1
When an object is heated the motion of the particles increases as the particles become more energetic. If it is cooled the motion of the particles decreases as they lose energy.
