Which statement about living organisms is correct?

• A. Composed of one or more cells
• B. They do not regulate their internal environment
• C. They do not respond to external stimuli
• D. They do not acquire nutrients from the environment

Answer: (A)

All living organisms are cellular, meaning they are composed of one or more cells. The cell is the basic unit of life, and cell theory states that organisms are made of cells and that new cells arise from existing ones. This is true for simple life, like bacteria and yeast, as well as complex life, like plants and animals. Some definitions even note that viruses aren’t cells, which is why the cellular nature is a defining criterion for what we call living.

The other statements would contradict fundamental features of life. Organisms regulate their internal environment to maintain stability, a process called homeostasis, so saying they do not regulate internal conditions is incorrect. They also respond to external stimuli, using sensory and signaling mechanisms to adapt to their surroundings, so a claim they do not respond is false. Finally, acquiring nutrients from the environment is essential for energy and growth; even organisms that produce their own food rely on environmental resources at some level, so stating they do not obtain nutrients from the environment is inaccurate.