accounting principles

Correct answer: A. The effect of an atmospheric element can depend on its location

Answer: A. The key idea is that the effect of a substance depends on its surroundings, especially its altitude and concentration. Ozone is the same chemical substance, O3, but its location changes its role. In the stratosphere, the ozone layer absorbs much of the Sun’s harmful ultraviolet radiation and helps protect living organisms. Near the ground, ozone is formed mainly through reactions involving pollutants in sunlight. It can irritate the respiratory system and harm plants, so it is treated as an air pollutant. B is wrong because ozone is not beneficial everywhere. C is wrong because ground-level ozone can affect health. D is wrong because ozone is not formed only in oceans. Memory cue: “High ozone protects; low ozone pollutes.”

Correct answer: A. Because it helps distinguish effects of dust, sea salt, smoke and industrial pollution

Answer: A. Fine solid particles suspended in air are often called aerosols or particulate matter. Their sources can be natural, such as wind-blown dust, sea salt, volcanic material, or biological particles, or human-made, such as smoke from fuel burning, construction dust, and industrial emissions. Separating the sources helps scientists identify what is causing poor air quality and decide which control measures are appropriate. It also helps compare their different effects on visibility, breathing, clouds, and radiation. B is wrong because particles have many sources. C is wrong because human activities release large amounts of particles. D is wrong because natural particles can influence the atmosphere. Memory cue: “Find the source before judging the solution.”

Correct answer: A. Because it remains available for respiration and nitrogen helps maintain atmospheric balance

Answer: A. Oxygen makes up roughly 21% of dry air, or about one-fifth, and this proportion is generally enough to support aerobic respiration in ordinary conditions. Organisms use oxygen to release energy from food. Nitrogen makes up most of the remaining air and dilutes oxygen, so the atmosphere is not an oxygen-rich mixture like nearly pure oxygen, in which combustion would be much more intense. B is wrong because many organisms require oxygen for aerobic respiration. C is wrong because oxygen is present in the atmosphere and in many compounds, not only in rocks. D is wrong because oxygen does not remove all water vapour. Memory cue: “Enough oxygen for life, enough nitrogen for moderation.”