An experiment was conducted to investigate the effect of simulated acid rain on plants. A mixture of sulfuric acid, nitric acid, and distilled water was used as acid rain. The pH of the prepared mixtures is 2.0, 3.0. 4.0, 5.0, and 6.0. After the treatment, it was observed that the chlorophyll content of the control (pH 7) is significantly higher than those with acid treatments. The plant height decreased significantly at all acidity levels with respect to the control set; the highest reduction was observed at pH 2.0. Which of the following describes the relationship between plant growth and pH?

• A. They are directly proportional
• B. They are inversely proportional
• C. They are equal
• D. They have no apparent relationship