Answer: B) global warming, resulting in warmer temperatures on Earth.
Step-by-step explanation:
Tundra is the coldest biome of the world. It exhibit very low temperature range and treeless plain with snow precipitation. The global warming is the phenomena which is related with rise in global temperature due to abundance of greenhouse gases into the atmosphere. These gases are released into the atmosphere by burning of fossil fuels, industrial gaseous release and deforestation. These gases traps the heat energy from sunlight making the atmospheric temperature warm. As a result of global warming the ice caps and snow bearing areas of the tundra biome will deplete. The melting of the ice will provide proper unfrozen soil for the growth of plants. Hence, new plants will increase in numbers due to global warming.