Concept:
Hazards are commonly classified by their cause into geological, water and climatic, biological, and environmental hazards.
Step 1:
Geological hazards include earthquakes, landslides and volcanoes; water and climatic hazards include floods and cyclones; biological hazards include epidemics and pest attacks.
Step 2:
Deforestation is the large-scale clearing of forests that degrades the environment, causes soil erosion and disturbs ecological balance. It is therefore grouped under environmental hazards.
Answer: Option (4) — Environmental hazards.