Why is treatment of dengue becoming a challenging task?

Treatment of cancer is:

Treatment of sewage involves

What is sewage treatment?

Why is the management of forest and wildlife resource considered as a challenging task?

Assertion : Secondary treatement of sewage is also called biological treatment while primary treatment is called physical treatment. Reason : Primary sewage treatment depends only upon sedimentation properties of materials present in sewage and filtration.

Why has the dodo become extinct?

For effective treatment of a disease