Final answer:
The dominant elements in the universe are hydrogen and helium, while on Earth, oxygen and silicon predominate in the crust. In living organisms, elements like carbon and nitrogen are essential, and terrestrial planets are composed mainly of oxygen compounds and iron.
Step-by-step explanation:
The question pertains to the identification of dominant elements in various environments such as the universe, Earth's crust, atmosphere, and the human body. In the universe, the most common elements are hydrogen and helium, with hydrogen comprising about 90% of atoms. On Earth, particularly in the crust, oxygen and silicon are the predominant elements, with oxygen making up 46.1% of the crust's mass and silicon making up 28.2%. In living organisms, essential elements include carbon, nitrogen, hydrogen, and oxygen, which are part of the biogeochemical cycles. Additionally, the terrestrial planets, such as Earth, are composed largely of oxygen compounds like silicates and feature abundant iron.