The Figure Below Shows the Predicted Distribution of Biomes Following

The figure below shows the predicted distribution of biomes following a 4ᵒ C increase in average global temperature.
What biome in North America, in addition to deserts, becomes more common and how can the change be explained?

A) Boreal forests expand because warmer temperatures reduce the extent of snow coverage and allow conifers to begin spring growth earlier.
B) Tundra expands because melted permafrost provides new habitat for cold-adapted grasses and herbs.
C) Topical forests expand because warmer temperatures expand tropical habitats, increase evaporation from the ocean surface, and provide the necessary rainfall.
D) Grasslands expand because warmer temperatures decrease average global rainfall, converting forest biomes to grasslands.