Explanation:

All statements are correct.

Nacreous clouds

• Nacreous clouds, also known as the Polar stratospheric clouds, are among the rarest and most stunning atmospheric phenomena.

• They are iridescent clouds that form only below -78C and usually develop in extremely cold air above Polar Regions.

• They are best known for the beautiful pastel light they reflect after sunset and before sunrise.

• Nacreous clouds are in indicator of especially cold air high in the atmosphere.

• Ozone layer: – The increased frequency of its occurrence signifies changes in the stratosphere that could have long-term implications for the ozone layer and climate.

• Formation:– It is formed when the temperatures in the stratosphere becomes so low and water particles turn into tiny ice crystals in the sky.

Hence option 3rd is correct.