Answer:
a. Cutting down all trees in a forest.
Step-by-step explanation:
Cutting of trees on the mass scale is called is known as deforestation. Deforestation is carried out to clear the forest land to use the same for the various purposes such as for the construction of industries, roads or planting crops. Deforestation creates ecological imbalance due to the increase of carbon dioxide concentration in the atmosphere causing greenhouse effect and global warming. Mass cutting of trees also causes soil erosion. Thus, the cutting of trees results in the loss of biological diversity of flora and fauna.