The section presents a question related to the composition of carbon dioxide (\( \mathrm{CO}_{2} \)). It asks which element is the main component of \( \mathrm{CO}_{2} \), providing four answer options: A. Carbon, B. Oxy, C. Hydrogen, and D. Nitơ. The key topics include chemical composition and elements, specifically focusing on carbon dioxide. The main entities involved are the chemical formula \( \mathrm{CO}_{2} \) and the elements carbon, oxygen, hydrogen, and nitrogen.