Which of the following trees is dangerous for environment?

The correct answer is Option 2.
Key Points

Effect of a Eucalyptus tree on the environment:

• It depletes the nutrients and moisture reserves of the soil and inhibits the undergrowth due to allelopathic properties.
• It replaced indigenous forests in several parts of the world.
• depleting food and shelter sources and therefore affecting animals and birds.
• The natural oils of the eucalyptus tree make it extremely flammable.
• Eucalyptus trees are native of Australia 

​whereas trees like banana, neem, and babool don't have a negative impact on the environment. Hence Option 2 is correct.