What is the colorless gas in the air that animals need to breathe?

The correct answer is oxygen, as it is the essential gas that animals require for survival. Oxygen plays a critical role in cellular respiration, a process through which cells convert glucose and other nutrients into energy. This energy is necessary for various bodily functions, including movement, growth, and repair.

In the atmosphere, oxygen makes up about 21% of the air we breathe, and it is vital for the majority of animal life on Earth. When animals inhale, they take in oxygen, which is then transported by the bloodstream to cells throughout the body. Cells use this oxygen to produce energy while releasing carbon dioxide as a byproduct, which animals then exhale.

Other gases, such as nitrogen and carbon dioxide, play important roles in the environment but do not serve as the primary gas for respiration in animals. Nitrogen, for instance, comprises about 78% of the atmosphere and is largely inert, meaning it does not participate in respiration. Carbon dioxide is a crucial component of the carbon cycle and is used by plants during photosynthesis but is not suitable for animal respiration. Hydrogen, while present in some compounds, is not found in a form that animals can use for breathing. Thus, oxygen is unequivocally the gas that animals need to breathe for