Which of the following is not caused by $UV-B$ radiation?

In the stratosphere,$UV$ rays act on $CFC$s to release which of the following atoms?

The presence of ozone $(O_3)$ in the atmosphere of Earth:

The main aim of the 'Earth Summit' organized in Brazil was:

Given below are two statements.
Statement $I$: Absorption of $UV$ radiations is directly proportional to the thickness of ozone.
Statement $II$: Ozone is generated by absorption of shorter wavelength of infrared radiations.
In the light of the above two statements,choose the correct answer from the options given below.

Why is an ozone hole formed over Antarctica? How will enhanced ultraviolet radiation affect us?