Final Answer:
C. Daily caffeine intake, quantitative; Alertness level, quantitative
Step-by-step explanation:
In option C, both daily caffeine intake and alertness level are classified as quantitative variables. Daily caffeine intake is measured in a numerical value, such as milligrams or grams, making it quantitative. Similarly, alertness level can be assessed on a numerical scale, such as a rating from 1 to 10. Quantitative variables involve numerical measurements and allow for mathematical operations like addition and subtraction. In this case, the use of numerical values for both daily caffeine intake and alertness level categorizes them as quantitative variables.
This distinction is important for statistical analysis, as it informs researchers about the nature of the data and the types of statistical tests that are appropriate for analysis. The consistency in measurement scales for both variables in option C aligns with the principles of quantitative data analysis.
Therefore, option C accurately defines the variables measured and their classification.