The correct answer is D. Carbon dioxide. Bacterial microorganisms require carbon dioxide as an essential element for their growth and survival. To determine the correct answer, you can eliminate options A and B based on basic knowledge about bacterial growth requirements. Bacteria do not rely on light for growth, so option A can be eliminated. Additionally, an acidic environment is generally unfavorable for bacterial growth and can inhibit their growth rather than promote it, so option B can also be eliminated. Considering option C, while body temperature is indeed suitable for the growth of certain bacteria, it is not an essential element for their growth. Finally, carbon dioxide (CO2) is essential for bacterial metabolism and serves as a carbon source for their growth. Therefore, option D is the correct answer.
