The correct answer is C. Forest
Step-by-step explanation
The forest is an ecosystem densely populated by trees and shrubs, in which animals, plants, microorganisms, insects and others coexist. In the air, it is purer thanks to the CO2 absorption of trees, they also protect the soil from direct sunlight. These ecosystems can be threatened by fires due to their high vegetation density that could be affected by fire unlike the desert, where there is no vegetation and the fire could easily be extinguished by winds in it, or in the Tundra where the vegetation is not so dense and the humidity is high, finally the sea, where the fire could not exist. So, the correct answer is C. Forest.