Explanation:
The Earth is comprised of many plates that float on the hot magma in the mantle layer. They are constantly moving but its so slow we can't feel it. A long time ago, all the land on Earth was connected in one big continent named Pangaea. As the plates have moved the land has separated forming the continents.
When plates come together they cause friction between them. This causes the plates to push up forming a mountain. This was how the Himalayan mountains were formed.
The correct answer is - ozone.
The ozone is essentially three molecules of oxygen, or O³. This gas is crucial for the life on the Earth because it is the one that manages to filter out big portion of the UV radiation from the Sun which is extremely harmful if its too strong, as it will contribute to the dying out of pretty much every living organism.
While the ozone layer in the stratosphere is very useful, the ozone in the lower parts of the troposphere is actually considered as pollutant. The reason why it is considered as pollutant is because it is very harmful if inhaled, and it also heavily damages the plants.
I would go with number one, because that's the only option that isn't negative.
