Which of the following is considered to be the optimum concentration of carbon dioxide for natural balance in atmosphere?

Detailed Solution:

The correct answer is “0.04%”.

The concentration of carbon dioxide (CO₂) in the Earth's atmosphere is typically around 0.03% to 0.04% (300-400 parts per million). This level is considered to be within the natural balance necessary for maintaining Earth's climate and supporting plant photosynthesis.