Dust in the air because the water molecules need something to condense around.
Ok this might not be the best answer but just by reading it, it may be unreliable because numbers do change over time
The best phrase is 'natural selection is a process that causes evolution '. Natural selection can also be referred to as selection pressures within a population that favour particular traits that enable the population to better adapt to its habitat. It's could be better camouflage, high sense of smell, and etcetera. These traits are preserved while those that cause disadvantage are diminished. This causes evolution of the population .
Usually during exercise, unlike during rest times the muscle cells need to respire more. So they need more oxygen and glucose for energy and the carbon-dioxide produced as waste must be removed quickly. So when person gets tired or breathes heavily during intensive workouts means they are in need of more oxygen. So the cells starts performing anaerobic(lactic acid ) respiration even though it releases less energy.
The example of the principle of the separation of powers is all of the choices given here. So the correct answer is D, all of the above.
