TOEFL Listening: TPO-TOEFL听力TPO - 83T_05J6Q73OL1NAR$

Why does the professor mention shrub expansion into other environments, such as semiarid grasslands? A. To suggest that new shrubland may not convert back to tundra B. To explain how shrubland can expand in warm climate C. To cite a similarity between the types of shrubs in semiarid grassland and tundra environments D. To explain how a biological loop can cause shrub expansion