Hilde is focusing her research-based informative essay on why Sweden is considered one of the most sustainable countries in the world. Hilde is particularly focused on Sweden’s carbon emissions. Hilde has written down the following research question: How has Sweden addressed its carbon emissions?

Which question is the most effective revision of Hilde’s research question?

A. What are the main contributors of carbon emissions in Sweden?
B. How did Sweden’s environmental policies reduce carbon emissions?
C. How do people in Sweden feel about the country’s carbon emissions?
D. What were Sweden’s carbon emissions over the past 10 years?