An economist believed that as nations become wealthier, they produce more greenhouse gases. He took a country and found both its gross domestic product (GDP) and the total tons of CO₂ emissions for each year over the past 50 years.

a. Generate a sentence that states the question the researcher is trying to answer.
b. List the variables and label them as independent and dependent.
c. Determine what type of study is being done: correlational, experimental, or quasi-experimental.
d. If the study is correlational or quasi-experimental, come up with a plausible confounding variable and explain how it affects both variables.