In the human eye,............. absorbs $UV-B$ radiation.

Why do fish die in water bodies infested with water hyacinth ($Eichhornia$ $crassipes$)?

Which of the following acts as a secondary pollutant?

The 'Blue Baby' syndrome is caused by .........

Exposure to a noise level of $............$ or more for a short period can damage the eardrums,leading to permanent hearing impairment. (in $,dB$)

What is the intensity of sound in normal conversation?