1. The problem asks which data sources can be used to collect bivariate data. 2. Bivariate data involves two variables that can be analyzed to find relationships or correlations. 3. Let's analyze each option: - a. Hours studied and test scores: This involves two variables, so it is bivariate data. - b. Age and height: This also involves two variables, so it is bivariate data. - c. Favorite food only: This is a single variable, so it is not bivariate data. - d. Number of pets: This is a single variable, so it is not bivariate data. 4. Therefore, options a and b are examples of bivariate data sources.