Which is most harmful for life on globe?

Nuclear Fallout

The correct answer is option 4. Nuclear Fallout.

The radioactive residue that is ejected into the upper atmosphere after a nuclear explosion or nuclear reaction that takes place in an unshielded facility is known as nuclear fallout, or simply fallout. It gets its name because it literally "falls out of the sky" after the explosion and shock wave have subsided. Nuclear fallout results in genetic mutation in humans and damage that cannot be prevented or remedied, but deforestation, soil erosion, and expanding deserts may be managed.