1 . Solution (c)

One Dobson Unit (DU) is defined to be 0.01 mm thickness at STP (standard temperature and pressure).

2 . Solution (a)

3 . Solution (a)
Jet planes are a major contributor to ozone depletion. Main source of aerosols is the emission of jet planes. These aerosols contains chlorofluorocarbons which react with ozone

4 . Solution (b)
Ozone is generated in the stratosphere as well as lower troposphere when Oxygen molecules react with Oxygen free radicals in presence of UV.

5 . Solution (d)
In May 1989, an international conference on ozone was held at Helsinki to revise the Montreal Protocol. As many as 80 countries agreed to have a total ban by 2000 on chemicals that cause ozone depletion. The agreement for CFC elimination is a major step towards environmental protection.

6 .  Solution (d)

7 . Solution (d)

8 .  Solution (b)

9 . Solution (c)

The Initiative is coordinated by Conservation International (CI), the International Union for Conservation of Nature (IUCN), and the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific, and Cultural Organization (IOC-UNESCO).

10 . Solution (b)