The student clearly states the independent variable as the brand of soft drinks and the dependent variable as the concentration of phosphoric acid in these drinks, with a detailed description of the method of analysis missing from the research question. The background theory is well-articulated, covering relevant concepts such as the Bronsted-Lowry acid theory and the principles of acid-base titration. The choice of techniques for measuring variables is explained, and the sampling technique is appropriately identified. However, the student fails to address controlled variables, safety, ethical, and environmental issues related to the investigation, and the methodology lacks sufficient detail for reproducibility. Overall, while the student demonstrates a solid understanding of the theoretical aspects and methodology, improvements are needed in specific areas for a more comprehensive investigation.
