Given below are two statements:
Statement I: Ozone has a protective role in the stratosphere but a harmful effect in the environment.
Statement II: Dobson unit is used to monitor the ozone layer's thickness.
In the light of the above statements, choose the correct answer from the options given below:

Correct option is A

The Correct answer is(a) Both Statement I and Statement II are true
Explanation:
.  Statement I is true. Ozone in the stratosphere is considered "good ozone" because it forms a protective layer that absorbs harmful ultraviolet (UV) radiation from the sun, protecting life on Earth. At ground level (in the troposphere), ozone is a harmful air pollutant and a major component of smog that can cause respiratory problems and damage crops and ecosystems.
.  Statement II is true. The Dobson Unit (DU) is the most common unit used to measure the total amount (thickness or column abundance) of ozone in a vertical column of the atmosphere. 
Information Booster:
. The 42nd Amendment also added fundamental duties to the Constitution upon the recommendations of the Swaran Singh Committee.
. The average thickness of the ozone layer is around 300 Dobson Units, which would form a layer about 3 millimeters thick if compressed to standard temperature and pressure.
. The discovery of the Antarctic ozone "hole" (areas with ozone levels below 220 DU) was made using instruments that measure ozone in Dobson units. 
Additional Knowledge:
Both Statement I and Statement II are false (Option B)
. This option is incorrect because both statements are factually correct descriptions of ozone's roles and measurement.
Statement I is true but Statement II is false (Option C)
. This option is incorrect because Statement II is a correct statement regarding the Dobson unit.
Statement I is false but Statement II is true (Option D)
. This option is incorrect because Statement I is a correct statement regarding the dual nature of ozone (good in stratosphere, bad at ground level).