TOEFL Listening: TPO-TOEFL听力TPO - 920OXV5NS5KI91D2R$

What is the lecture mainly about? A. Factors involved in the increased growth of shrubs in Arctic Alaska B. How temperature increases might be affecting the permafrost in Arctic Alaska C. Why nutrient production of microbes in the soil in Arctic Alaska is declining D. Reasons that grasslands are turning into tundra in Arctic Alaska